CN117580473A

CN117580473A - Article with tubular aerosol-forming substrate

Info

Publication number: CN117580473A
Application number: CN202280045697.7A
Authority: CN
Inventors: G·坎皮特利; F·费德里; M·法里纳
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2021-07-07
Filing date: 2022-07-07
Publication date: 2024-02-20
Also published as: CN117597035A

Abstract

An aerosol-generating article for generating an inhalable aerosol upon heating is provided comprising a plurality of components comprising an aerosol-forming substrate. The aerosol-forming substrate is in the form of a hollow tubular section 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 with thermally conductive particles allows for faster to first puffs, improved aerosol extraction efficiency and lighter weight aerosol-generating articles.

Description

Article with tubular aerosol-forming substrate

The present disclosure relates to an aerosol-generating article comprising a tubular aerosol-forming substrate. The present disclosure also relates to a method of manufacturing an aerosol-forming substrate for such an article and an aerosol-generating system.

Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than combusted are known in the art. Generally, in such heated smoking articles, an aerosol is generated by transferring heat from a heat source to a physically separate aerosol-generating substrate or material that may be positioned in contact with, inside, around or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in air drawn through the aerosol-generating article. As the released compound cools, the compound condenses to form an aerosol.

A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices in which an aerosol is generated by transferring heat from one or more electric heater elements of the aerosol-generating device to an aerosol-generating substrate of a heated aerosol-generating article. For example, electrically heated aerosol-generating devices have been proposed which comprise an internal heating plate adapted to be inserted into an aerosol-generating substrate. It is also known to use aerosol-generating articles in combination with external heating systems. For example, WO-A-2020/115151 describes the provision of external heating elements arranged around the periphery of an aerosol-generating article when the aerosol-generating article is received in A cavity of an aerosol-generating device. As an alternative WO-A-2015/176898 proposes an inductively heatable aerosol-generating article comprising an aerosol-generating substrate and A susceptor arranged within the aerosol-generating substrate.

In general, it may be difficult to provide efficient heating of the aerosol-generating substrate across the entire strip of the substrate. The portion of the substrate closest to the heating element will inevitably be heated most effectively, while imperfect transfer of heat through the substrate will mean that the portion of the substrate furthest from the heating element may not be heated effectively. Thus, aerosol generation from those portions of the substrate that are not effectively heated is not optimal, and in some cases, portions of the substrate may not reach sufficiently high temperatures at all during use to generate an aerosol. For example, in the case of using an external heating element to heat a strip of aerosol-generating substrate, as described above, the central portion of the strip of aerosol-generating substrate is less likely to generate as much aerosol as the outer portion of the strip, and in some cases may not generate any aerosol. In summary, aerosol generation from an aerosol-generating rod may thus be inefficient, wherein a portion of the aerosol-generating substrate may be wasted.

In addition, aerosol-generating substrates typically do not immediately generate an aerosol upon activation of the heating element. This is because there is a pre-heating time after activation of the heating element during which the aerosol-generating substrate is heated to the temperature required for aerosol generation. Thus, there may be a relatively long duration between activation of the heating element and generation of the organoleptically acceptable aerosol for inhalation by the user.

It is therefore desirable to provide an aerosol-generating article having an aerosol-generating substrate which is adapted to provide more efficient aerosolization of the aerosol-generating substrate and to reduce wastage of substrate material such as tobacco. It is also desirable to provide an aerosol-generating article that can achieve a relatively short warm-up time so that a sensorially acceptable aerosol can be delivered to the user shortly after starting heating the aerosol-generating substrate. It is also desirable to provide an aerosol-generating article that can provide optimized aerosol delivery from an aerosol-generating substrate. It is particularly desirable to provide an aerosol-generating article having a relatively simple design such that it can be manufactured and incorporated into existing product designs in a cost-effective manner. It is also desirable to provide an article that can be easily adapted such that it can be heated in various types of heating devices, including induction heating devices and resistive heating devices.

Known aerosol-forming substrates generally have a relatively low thermal conductivity. The low thermal conductivity of the aerosol-forming substrate may lead to a relatively large temperature gradient in the aerosol-forming substrate during use. This may mean that the part of the aerosol-forming substrate located furthest from the heater element does not reach high temperatures and therefore does not release as much volatile compounds as if the aerosol-forming substrate had a higher thermal conductivity. In other words, the low thermal conductivity of the aerosol-forming substrate may undesirably result in low efficiency of use of the aerosol-forming substrate.

In accordance with the present disclosure, an aerosol-generating article for generating an inhalable aerosol upon heating is provided. The aerosol-generating article may comprise a plurality of components comprising an aerosol-forming substrate. The aerosol-forming substrate may be in the form of a hollow tubular section, which preferably defines 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 preferably comprises a plurality of thermally conductive particles and an aerosol-former.

For example, an aerosol-generating article for generating an inhalable aerosol upon heating may be provided, the aerosol-generating article comprising a plurality of components 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, and wherein the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-forming agent.

The use of tubular geometry for aerosol-forming substrates may help avoid the thermal gradient effect of heating the substrate. With tubular geometry, the substrate has no core and the aerosol-forming material is concentrated at the region of the substrate that is heated either internally or externally. This enables a significant increase in extraction efficiency, which in turn may reduce the total amount of matrix required for the user experience. The reduced mass of the substrate will reduce the heating inertia and thus the time taken to heat to a sufficient temperature and thus the time to first draw. The use of a thermally conductive matrix can significantly increase the advantages obtained by employing a tubular matrix geometry. The increase or enhancement of the thermal conductivity of the matrix caused by the presence of the thermally conductive particles may further reduce the inertia of the matrix and may further shorten the time to first pumping and increase the overall extraction efficiency. The weight of the matrix can be even further reduced by selecting specific thermally conductive particles, such as graphite or expanded graphite. The reduction in the total mass of the aerosol-forming substrate required for a sufficient user experience has a number of advantages, including a reduction in the overall thermal inertia and a reduction in the weight of the aerosol-generating article comprising the substrate. The reduction in weight of the article may reduce shipping costs and reduce the energy involved in shipping, and may also enjoy tax benefits in certain jurisdictions.

The aerosol-generating article according to the invention may be particularly advantageously used in aerosol-generating systems employing progressive or zonal heating. The aerosol-generating article according to the invention may also be particularly advantageous for use in aerosol-generating systems employing suction on demand heating.

The aerosol-forming substrate may comprise between 5 and 95 wt% [ wt% ] of thermally conductive particles on a dry weight basis, for example between 10 and 90 wt% of thermally conductive particles. The aerosol-forming substrate may comprise between 7 and 60 wt% aerosol-forming agent on a dry weight basis. The aerosol-forming substrate may comprise between 2 and 20% by weight fibres on a dry weight basis. The aerosol-forming substrate may comprise between 2 and 10 wt% binder on a dry weight basis. Each of the thermally conductive particles may be composed of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

Thus, an aerosol-forming substrate may be provided comprising, on a dry weight basis: between 10 and 90 wt% thermally conductive particles; between 7 and 60 wt% aerosol former; between 2 and 20 weight percent fiber; and between 2 and 10 wt% of a binder, wherein each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

The aerosol-generating article may comprise on a dry weight basis: between 5 and 95 wt%, e.g. between 10 and 90 wt%, of thermally conductive particles, each of the thermally conductive particles having a thermal conductivity of at least 1W/(mK). The thermal conductivity may be measured in at least one direction of the particles. Thermal conductivity can be measured at a temperature of 25 degrees celsius.

Wherein the term "thermally conductive particles" is used to refer to particles comprising carbon, such as particles comprising or consisting of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, the thermally conductive particles may be referred to as carbon particles or carbon-containing particles.

Advantageously, the thermally conductive particles may increase the thermal conductivity of the aerosol-forming substrate. The increased thermal conductivity of the matrix may provide a more uniform temperature distribution throughout the matrix during use. This may result in a greater proportion of the aerosol-forming substrate reaching a sufficiently high temperature to release volatile compounds and thus in greater efficiency of use of the aerosol-forming substrate. Further, the increased thermal conductivity of the substrate may allow the heater (e.g., a heating blade configured to heat the substrate) to operate at a lower temperature and thus require less power. Still further, the increased thermal conductivity of the matrix may allow the heater to heat the matrix to a temperature that releases the volatile compounds in a shorter time. Thus, the increased thermal conductivity may reduce the time required for a user to form an inhalable aerosol.

Advantageously, one or both of the fibers and the binder may increase the tensile strength of the material forming the aerosol-forming substrate. The increased tensile strength may, for example, allow for the production of a sheet of aerosol-forming material using existing production machinery, which may be formed into a tube to form an aerosol-forming substrate.

The aerosol-forming substrate may have a thermal conductivity of at least 0.05, 0.1, 0.15, 0.2, 0.22, 0.3, 0.4 or 0.5W/(mK) at 25 degrees celsius in at least one direction or in all directions. The thermal conductivity can be measured when the moisture content of the matrix is between 0 and 20%, or between 5 and 15%, for example around 10%. The thermal conductivity may be measured when the matrix comprises between 0 and 20 wt.%, or between 5 and 15 wt.%, for example around 10 wt.% of water. The moisture or water content of the matrix can be measured using titration methods. The moisture or water content of the matrix can be measured using the karl fischer method.

Optionally, some or all of the thermally conductive particles comprise at least 10, 30, 50, 70, 90, 95, 98, or 99 wt% carbon.

Optionally, some or all of the thermally conductive particles are graphite particles. Optionally, some or all of the thermally conductive particles are expanded graphite particles. Optionally, some or all of the thermally conductive particles are graphene particles. Optionally, some or all of the thermally conductive particles are carbon nanotubes or carbon nanotube particles. Optionally, some or all of the thermally conductive particles are charcoal particles. Optionally, some or all of the thermally conductive particles are diamond particles, such as synthetic diamond particles. Advantageously, such materials may have a relatively high thermal conductivity.

The expanded graphite may have a particle size of less than 2, 1.8, 1.5, 1.2, 1, 0.8 or 0.5, 0.2, 0.1, 0.05, 0.02 grams/cubic centimeter (g/cm) ³ ) Is a density of (3). The expanded graphite may have a particle size of greater than 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, or 1.8 grams/cubic centimeter (g/cm) ³ ) Is a density of (3). The expanded graphite may have a concentration of 0.01 to 3, 0.01 to 2, 0.01 to 1.8, 0.01 to 1.5, 0.01 to 1.2, 0.01 to 1, 0.01 to 0.8, 0.01 to 0.5, 0.02 to 3, 0.02 to 2, 0.02 to 1.8, 0.02 to 1.5, 0.02 to 1.2, 0.02 to 1, 0.02 to 0.8, 0.02 to 0.5, 0.01 to 3, 0.05 to 2, 0.05 to 1.8, 0.05 to 1.5, 0.05 to 1.2, 0.05 to 1, 0.05 to 0.8, 0.05 to 0.5g/cm ³ 0.1 to 3, 0.1 to 2, 0.1 to 1.8, 0.1 to 1.5, 0.1 to 12, 0.1 to 1, 0.1 to 0.8, 0.1 to 0.5, 0.2 to 3, 0.2 to 2, 0.2 to 1.8, 0.2 to 1.5, 0.2 to 1.2, 0.2 to 1, 0.2 to 0.8, 0.2 to 0.5, 0.5 to 3, 0.5 to 2, 0.5 to 1.8, 0.5 to 1.5, 0.5 to 1.2, 0.5 to 1, 0.5 to 0.8, 0.8 to 3, 0.8 to 2, 0.8 to 1.8, 0.8 to 1.5, 0.8 to 1.2, 0.8 to 1 g/cc (g/cm) ³ ) Density of the two.

Optionally, some or all of the thermally conductive particles comprise a metal in accordance with aspects in which each of the thermally conductive particles does not necessarily consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond. Alternatively or additionally, some or all of the thermally conductive particles comprise an alloy. Alternatively or additionally, some or all of the thermally conductive particles comprise an intermetallic compound. Advantageously, such materials may have a relatively high thermal conductivity.

Optionally, in accordance with alternative aspects in which each of the thermally conductive particles does not necessarily consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond, some or all of the thermally conductive particles comprise one or more of silicon carbide, silver, copper, gold, aluminum nitride, aluminum, tungsten, and boron nitride. Optionally, some or all of the thermally conductive particles are silicon carbide particles. Optionally, some or all of the thermally conductive particles are silver particles. Optionally, some or all of the thermally conductive particles are copper particles. Optionally, some or all of the thermally conductive particles are gold particles. Optionally, some or all of the thermally conductive particles are aluminum nitride particles. Optionally, some or all of the thermally conductive particles are aluminum particles. Optionally, some or all of the thermally conductive particles are tungsten particles. Optionally, some or all of the thermally conductive particles are boron nitride particles. Advantageously, such materials may have a relatively high thermal conductivity.

The thermally conductive particles may each have a "particle size". The meaning of the term "particle size" and the method of measuring particle size will be set forth later.

The thermally conductive particles may be characterized by a particle size distribution. The particle size distribution may have a number D10, D50 and D90 particle sizes. The number D10 particle size is defined as such that 10% of the particles have a particle size less than or equal to the number D10 particle size. Similarly, the number D50 particle size is defined such that 50% of the particles have a particle size less than or equal to the number D50 particle size. Thus, the number D50 of particle sizes may be referred to as the median particle size. The number D90 particle size is defined as such that 90% of the particles have a particle size less than or equal to the number D90 particle size. Thus, if there are 1,000 particles in the distribution and the particles are ordered in ascending order of particle size, then the expected number D10 of particles sizes is approximately equal to the 100 th particle size, the number D50 of particles sizes is approximately equal to the 500 th particle size, and the number D90 of particles sizes is approximately equal to the 900 th particle size.

The particle size distribution may have volume D10, D50 and D90 particle sizes. The volume D10 particle size is defined such that the sum of the volumes of particles having a particle size less than or equal to the volume D10 particle size is 10% of the sum of the volumes of all particles. Similarly, the volume D50 particle size is defined such that the sum of the volumes of particles having a particle size less than or equal to the volume D50 particle size is 50% of the sum of the volumes of all particles. And the volume D90 particle size is defined such that the sum of the volumes of particles having a particle size less than or equal to the volume D90 particle size is 90% of the sum of the volumes of all particles.

Optionally, the thermally conductive particles have a particle size distribution having a number D10 of particle sizes, wherein the number D10 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a number D10 of particle sizes, wherein the number D10 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

A compromise must be made in deciding the size of the particles. Larger thermally conductive particles may advantageously increase the thermal conductivity of the aerosol-forming substrate more than smaller thermally conductive particles. However, larger thermally conductive particles reduce the space available for aerosol-forming material in the matrix.

Optionally, the thermally conductive particles have a particle size distribution having a number D50 of particle sizes, wherein the number D50 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a number D50 of particle sizes, wherein the number D50 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Optionally, the thermally conductive particles have a particle size distribution having a number D90 of particle sizes, wherein the number D90 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a number D90 of particle sizes, wherein the number D90 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Optionally, the thermally conductive particles have a particle size distribution having a number D10 particle size and a number D90 particle size, wherein the number D90 particle size is no greater than 50, 40, 30, 20, 10, or 5 times the number D10 particle size.

Optionally, the thermally conductive particles have a particle size distribution having a number D10 particle size and a number D90 particle size, wherein the number D90 particle size is at least 1.5, 2, 3, 5, 10, or 20 times the number D10 particle size.

A compromise in particle size distribution may need to be made. A tighter particle size distribution, such as that characterized by a smaller ratio between D90 and D10 particle sizes, may advantageously provide a more uniform thermal conductivity throughout the aerosol-forming substrate. This is because the particle size variation will be smaller in different locations in the matrix. This may advantageously allow for more efficient use of the aerosol-forming material throughout the aerosol-forming substrate. However, a tighter particle size distribution may be disadvantageously more difficult to achieve and more expensive. The inventors have found that the above particle size distribution can provide the best compromise between these two factors.

Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Optionally, the thermally conductive particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

Optionally, the thermally conductive particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

Optionally, the thermally conductive particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

It may be particularly preferred that the thermally conductive particles have a particle size distribution with a volume D10 particle size between 1 and 20 micrometers. Alternatively or additionally, it may be particularly preferred that the thermally conductive particles have a particle size distribution with a volume D90 particle size between 50 and 300 micrometers or between 50 and 200 micrometers.

Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, wherein the volume D90 particle size is no greater than 50, 40, 30, 20, 10, or 5 times the volume D10 particle size.

Optionally, the thermally conductive particles have a particle size distribution having a volume D10 particle size and a volume D90 particle size, wherein the volume D90 particle size is at least 1.5, 2, 3, 5, 10, or 20 times the volume D10 particle size.

As explained above, a compromise must be made in terms of particle size distribution, and the inventors have found that the above particle size distribution can provide the best compromise.

Optionally, each of the thermally conductive particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns. Optionally, each of the thermally conductive particles has a particle size of no greater than 1,000, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. It may be particularly preferred that each of the thermally conductive particles have a particle size of at least 1 micron. Alternatively or additionally, it may be particularly preferred that each of the thermally conductive particles have a particle size of not more than 300 microns. Particles smaller than 1 micron may be difficult to handle during manufacturing. In addition, particles smaller than 1 micron may be more likely to pass through a filter in an aerosol-generating article comprising an aerosol-forming substrate. Particles larger than 300 microns may occupy a significant amount of space in the matrix that could otherwise be used for aerosol-forming materials. Thus, it may be particularly preferred that each of the thermally conductive particles have a particle size of at least 1 micron or a particle size of no more than 300 microns or both.

Optionally, each of the thermally conductive particles has three mutually perpendicular dimensions, a largest dimension of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a smallest dimension of the three dimensions. Optionally, each of the thermally conductive particles has three mutually perpendicular dimensions, a largest dimension of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a second largest dimension of the three dimensions. Optionally, each of the thermally conductive particles is substantially spherical. Advantageously, the orientation of the substantially spherical particles does not affect the thermal conductivity of the matrix as much as the orientation of the non-spherical particles. Thus, the use of more spherical particles may result in less variability between different matrices in which the orientation of the particles is uncontrolled. In addition, substantially spherical particles may be easier to characterize.

Optionally, the thermally conductive particles comprise at least 10, 20, 50, 100, 200, 500, or 1000 particles. Advantageously, a greater number of particles in the aerosol-forming substrate may allow for a more uniform thermal conductivity of the substrate.

Optionally, the matrix comprises at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 weight percent thermally conductive particles on a dry weight basis. Optionally, the matrix comprises no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, or 15 weight percent thermally conductive particles on a dry weight basis. Optionally, the matrix comprises between 10 to 90, 20 to 90, 30 to 90, 40 to 90, 50 to 90, 60 to 90, 70 to 90, 80 to 90, 10 to 80, 20 to 80, 30 to 80, 40 to 80, 50 to 80, 60 to 80, 70 to 80, 10 to 70, 20 to 70, 30 to 70, 40 to 70, 50 to 70, 60 to 70, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 10 to 40, 20 to 40, 30 to 40, 10 to 30, 20 to 30, or 10 to 20 weight percent thermally conductive particles on a dry weight basis. It may be particularly preferred that the matrix comprises between 50 and 90 wt.%, or more preferably between 60 and 90 wt.%, or even more preferably between 65 and 85 wt.% of thermally conductive particles on a dry weight basis.

A compromise may need to be made in terms of the weight percentage of thermally conductive particles in the matrix. Increasing the weight percent of particles in the aerosol-forming substrate may advantageously increase the thermal conductivity of the substrate. However, increasing the weight percent of particles in the aerosol-forming substrate also reduces the available space for one or more of the aerosol-former, binder, and fibers, thus potentially producing a substrate that forms less aerosol or has less tensile strength.

Optionally, the matrix comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50 or 55 wt% aerosol former on a dry weight basis. Optionally, the matrix comprises no more than 55, 50, 45, 40, 35, 30, 25, 20 or 15 wt% aerosol former on a dry weight basis. Optionally, the matrix comprises between 7 to 60, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 7 to 50, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 7 to 40, 10 to 40, 20 to 40, 30 to 40, 7 to 30, 10 to 30, 20 to 30, 7 to 20, 10 to 20, or 7 to 10 weight percent aerosol former on a dry weight basis. It may be particularly preferred that the matrix comprises between 15 and 25 wt% aerosol former on a dry weight basis.

Optionally, the aerosol former comprises or consists of one or more of the following: polyhydric alcohols such as propylene glycol, polyethylene glycol, triethylene glycol, 1, 3-butanediol, and glycerol; esters of polyhydric alcohols, such as glycerol mono-, di-or triacetate; and aliphatic esters of monocarboxylic, dicarboxylic or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Optionally, the aerosol-forming substrate comprises one or both of glycerol and glycerin.

Optionally, the matrix comprises at least 2, 4, 6, 8, 10, 12, 14, 16 or 18 weight percent fibers on a dry weight basis. Optionally, the matrix comprises no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4 weight percent fibers on a dry weight basis. Optionally, the matrix comprises between 4 to 20, 6 to 20, 8 to 20, 10 to 20, 12 to 20, 14 to 20, 16 to 20, 18 to 20, 2 to 18, 4 to 18, 6 to 18, 8 to 18, 10 to 18, 12 to 18, 14 to 18, 16 to 18, 2 to 16, 4 to 16, 6 to 16, 8 to 16, 10 to 16, 12 to 16, 14 to 16, 2 to 14, 4 to 14, 6 to 14, 8 to 14, 10 to 14, 12 to 14, 2 to 12, 4 to 12, 6 to 12, 8 to 12, 10 to 12, 2 to 10, 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, or 2 to 4 weight percent of the fiber on a dry weight basis. It may be particularly preferred that the matrix comprises between 2 and 10% by weight of fibres on a dry weight basis.

Optionally, the fibers are cellulosic fibers. Advantageously, cellulose fibers are less expensive and can increase the tensile strength of the matrix.

Optionally, each fiber has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a smallest dimension of the three dimensions. Optionally, each fiber has three mutually perpendicular dimensions, a largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10, or 20 times larger than a second largest dimension of the three dimensions.

Optionally, the matrix comprises at least 4, 6 or 8 wt% binder on a dry weight basis. Optionally, the matrix comprises no more than 8, 6 or 4 wt% binder on a dry weight basis. Optionally, the matrix comprises between 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, 2 to 4 weight% binder on a dry weight basis. It may be particularly preferred that the matrix comprises between 2 and 10 wt.% binder on a dry weight basis.

Suitable binders are well known in the art and include, but are not limited to, natural pectins, such as fruit, citrus or tobacco pectins; guar gums, such as hydroxyethyl guar and hydroxypropyl guar; locust bean gums, such as hydroxyethyl and hydroxypropyl locust bean gums; an alginate; starches, such as modified starches or derivatized starches; cellulose, such as methyl cellulose, ethyl hydroxymethyl cellulose, and carboxymethyl cellulose; tamarind gum; dextran; pralan (pulullon); konjaku flour; xanthan gum, and the like. Especially preferred for the binder may be guar gum or include guar gum. It may be particularly preferred that the binder comprises or consists of one or more of carboxymethyl cellulose or hydroxypropyl cellulose or a gum such as guar gum.

Optionally, the thermally conductive particles are substantially uniformly distributed throughout the aerosol-forming substrate. Optionally, the aerosol-forming agent is substantially uniformly distributed throughout the aerosol-forming substrate. Optionally, the fibers are substantially uniformly distributed throughout the aerosol-forming substrate. Optionally, the binder is substantially uniformly distributed throughout the aerosol-forming substrate. Advantageously, a uniform distribution of the components of the matrix may result in a matrix having more spatially uniform properties. For example, a substantially uniform distribution of thermally conductive particles may result in a matrix having a substantially uniform thermal conductivity. As another example, a substantially uniform distribution of binder or fibers may result in a matrix having a substantially uniform tensile strength.

Optionally, the substrate comprises nicotine. Optionally, the substrate comprises at least 0.01, 1, 2, 3 or 4% by weight nicotine on a dry weight basis. Optionally, the substrate comprises no more than 5, 4, 3, 2 or 1% by weight nicotine on a dry weight basis. Optionally, the substrate comprises between 0.01 to 5, 1 to 5, 2 to 5, 3 to 5, 4 to 5, 0.01 to 4, 1 to 4, 2 to 4, 3 to 4, 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1% by weight nicotine on a dry weight basis. It may be particularly preferred that the substrate comprises between 0.5 and 4% by weight of nicotine on a dry weight basis.

Optionally, the nicotine is substantially uniformly distributed throughout the aerosol-forming substrate.

Optionally, the matrix comprises an acid. Optionally, the matrix comprises at least 0.01, 1, 2, 3 or 4 wt% acid on a dry weight basis. Optionally, the matrix comprises no more than 5, 4, 3, 2 or 1 wt% acid on a dry weight basis. Optionally, the matrix comprises between 0.01 to 5, 1 to 5, 2 to 5, 3 to 5, 4 to 5, 0.01 to 4, 1 to 4, 2 to 4, 3 to 4, 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1 weight percent acid on a dry weight basis. It may be particularly preferred that the matrix comprises between 0.5 and 5% by weight of acid on a dry weight basis.

Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid and levulinic acid.

Optionally, the acid is substantially uniformly distributed throughout the aerosol-forming substrate.

Optionally, the matrix comprises at least one plant-derived material. Optionally, the matrix comprises at least 0.01, 1, 2, 5, 10 or 15 wt% of the at least one plant-derived material on a dry weight basis. Optionally, the matrix comprises no more than 20, 15, 10, 5, 2 or 1 wt% of the at least one plant-derived material on a dry weight basis. Optionally, the matrix comprises between 0.01 to 20, 1 to 20, 2 to 20, 5 to 20, 10 to 20, 15 to 20, 0.01 to 15, 1 to 15, 2 to 15, 5 to 15, 10 to 15, 0.01 to 10, 1 to 10, 2 to 10, 5 to 10, 0.01 to 5, 1 to 5, 2 to 5, 0.01 to 2, 1 to 2, 0.01 to 1 weight percent of the at least one plant-derived material on a dry weight basis. It may be particularly preferred that the matrix comprises between 1 and 15% by weight of said at least one plant-derived material on a dry weight basis.

Optionally, the at least one plant-derived material comprises or consists of one or both of clove and rosemary.

Optionally, the at least one plant-derived material is substantially uniformly distributed throughout the aerosol-forming substrate.

Optionally, the matrix comprises at least one flavoring agent. Optionally, the matrix comprises at least 0.1, 1, 2 or 5 wt% of said at least one flavoring agent on a dry weight basis. Optionally, the matrix comprises no more than 10, 5, 2 or 1 wt% of said at least one flavoring agent on a dry weight basis. Optionally, the matrix comprises between 0.1 to 10, 1 to 10, 2 to 10, 5 to 10, 0.1 to 5, 1 to 5, 2 to 5, 0.1 to 2, 1 to 2, 0.1 to 1 weight% of said at least one flavoring agent on a dry weight basis. It may be particularly preferred that the matrix comprises between 0.1 and 5% by weight of said at least one flavouring agent on a dry weight basis.

Optionally, the at least one flavoring agent is present as a coating, such as a coating on one or more other components of the aerosol-forming substrate. Alternatively or additionally, the at least one flavour is substantially evenly distributed throughout the aerosol-forming substrate.

Optionally, the aerosol-forming substrate comprises at least one organic material such as tobacco. Optionally, the at least one organic material comprises one or more of herb leaf, tobacco leaf rib segment, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the at least one organic material is substantially uniformly distributed throughout the aerosol-forming substrate.

The substrate may comprise less than 10, 5, 3, 2 or 1% by weight tobacco on a dry weight basis. Optionally, the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

The tubular section of the aerosol-forming substrate may be described as a rod. Thus, a strip of aerosol-forming substrate may be provided.

The aerosol-forming substrate is preferably in the form of a tube having an outer diameter, an inner diameter and a length, wherein the length of the tube is between 5mm and 100mm, the outer diameter is between 3mm and 20mm and the inner diameter is between 2.5mm and 19.5 mm. The length of the tube may be between 8mm and 25mm, the outer diameter of the tube may be between 6mm and 8mm, and the inner diameter of the tube may be between 5mm and 7.9 mm.

The susceptor element may be located within a strip of aerosol-forming substrate. The susceptor element may be an elongated susceptor element. The susceptor element may extend longitudinally within the strip of aerosol-forming substrate, for example in contact with the inner surface of the tubular aerosol-generating substrate. The strip may be generally cylindrical in shape, such as right cylindrical. The susceptor element may extend all the way to the downstream end of the strip of aerosol-forming substrate. The susceptor element may extend all the way to the upstream end of the strip of aerosol-forming substrate. The susceptor element may have substantially the same length as the strip of aerosol-forming substrate. The susceptor element may extend from an upstream end to a downstream end of the strip of aerosol-forming substrate. The susceptor element may be in the form of a needle, a strip or a blade. The susceptor element may have a length of between 5 and 15, 6 and 12, or 8 and 10 millimeters. The susceptor element may have a width of between 1 and 5 mm. The susceptor element may have a thickness of between 0.01 and 2, 0.5 and 2, or 0.5 and 1 millimeter.

Alternatively, no susceptor material may be present in the aerosol-forming substrate or in the strip of aerosol-forming substrate.

Optionally, some or each of the thermally conductive particles may be inductively heatable, e.g. inductively heatable to a temperature of at least 100, 150 or 200 degrees celsius. Optionally, some or each of the thermally conductive particles comprises or consists of one or more susceptor materials. Advantageously, this may allow the thermally conductive particles to be inductively heated. The thermally conductive particles may constitute or be the only susceptor material present in the aerosol-forming substrate or in the strips of the aerosol-forming substrate. That is, there may be no susceptor element in the aerosol-forming substrate or in the strip of aerosol-forming substrate other than the thermally conductive particles or the carbon particles.

Suitable susceptor materials include, but are not limited to: carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel-containing compounds, composite materials of titanium and metallic materials. Suitable susceptor materials may include ferromagnetic materials, such as ferritic iron, ferromagnetic alloys such as ferromagnetic or stainless steel, ferromagnetic particles, and ferrites. Suitable susceptor materials may be or include aluminum. The susceptor material preferably comprises more than 5%, preferably more than 20%, more preferably more than 50% or more than 90% of ferromagnetic or paramagnetic material. Preferred susceptor materials may include metals, metal alloys, or carbon.

Particularly preferred susceptor materials may be or include carbon, carbon-based materials, graphene, graphite or expanded graphite. Advantageously, such materials have relatively high thermal conductivity, relatively low density, and can be inductively heated.

Optionally, the aerosol-forming substrate has a thermal conductivity of greater than 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.25, 1.5, 2, 5, 10, 20, 50, 100, 200, or 500W/(mK) at 25 degrees celsius in at least one direction.

Optionally, the aerosol-forming substrate has a composition of no greater than 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1050, 1000, 950, 900, 850, 800, 750, 700, 650, or 600kg/m ³ Is a density of (3). Optionally, the aerosol-forming substrate has 600 to 1400, 800 to 1200, or 900 to 1100kg/m ³ Density of the two. Advantageously, reducing the density of the matrix may reduce the transportation cost of the matrix.

Optionally, the aerosol-forming substrate has a moisture content of between 1 and 20, or 3 and 15 wt%. The moisture content may be measured after equilibration at 50% relative humidity for 48 hours at 20 degrees celsius. Optionally, the aerosol-forming substrate comprises between 1 and 20, or 3 and 15 wt% water. The moisture or water content of the matrix can be measured using titration methods. The moisture or water content of the matrix can be measured using the karl fischer method.

Optionally, the aerosol-forming substrate is formed from a sheet of aerosol-forming material which is rolled to form the tubular section. Thus, the hollow tubular section may be a rolled sheet of aerosol-forming material, such as a rolled sheet of homogenized tobacco material or such as a rolled sheet of smokeless aerosol-forming material.

The aerosol-forming substrate may have a thickness equal to a sheet of single layer aerosol-forming material. The aerosol-forming substrate may have a thickness equal to two or more sheets. The sheet of aerosol-forming material may have a thickness of at least 5, 10, 20, 50, 100, 150 or 200 microns. Optionally, the sheet or strip may have a thickness of no greater than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the sheet may have a thickness of between 100 and 350, or 150 and 300 microns.

Optionally, the sheet of aerosol-forming material has a particle size of at least 20, 50 or 100g/m ² Gram weight per square meter. Optionally, the sheet or strip has a bulk of no more than 300g/m ² Gram weight per square meter. Optionally, the sheet has 20 to 300, 50 to 250, or 100 to 250g/m ² Gram weight per square meter.

Optionally, the sheet has at least 0.1, 0.2, 0.3 or 0.5g/m ³ Is a density of (3). Optionally, the sheet has a weight of no more than 2, 1.5, 1.2 or 1g/m ³ Is a density of (3). Optionally, the sheet has a weight of 0.1 to 2, 0.2 to 2, 0.3 to 1.5, or 0.3 to 1.2g/m ³ Density of the two.

The hollow tubular section may be an extruded tube of aerosol-forming material, such as an extruded tube of homogenized tobacco material or such as an extruded tube of non-tobacco aerosol-forming material.

The aerosol-generating article may be in the form of a rod and may comprise a plurality of components assembled within a wrapper or housing, the plurality of components comprising an aerosol-forming substrate.

Optionally, the aerosol-generating article comprises a front filter segment. Optionally, the aerosol-generating article comprises a first hollow tube, for example a first hollow acetate tube. Optionally, the aerosol-generating article comprises a second hollow tube, for example a second hollow acetate tube. Optionally, the second hollow tube comprises one or more ventilation holes. Optionally, the aerosol-generating article comprises an oral filter segment filter. Optionally, the aerosol-generating article comprises a wrapper, for example a paper wrapper.

Optionally, the front filter segment is disposed at the most upstream end of the article. Optionally, an aerosol-forming substrate is disposed downstream of the front filter section. Optionally, the first hollow tube is arranged downstream of the aerosol-forming substrate. Optionally, a second hollow tube is arranged downstream of the first hollow tube. Optionally, the mouth filter segment filter is disposed downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth filter segment filter is disposed at the most downstream end of the article. Optionally, the downstream-most end of the article (which may be referred to as the mouth end of the article) may be configured to be inserted into the mouth of a user. The user may be able to inhale, for example, directly on the mouth end of the article.

Optionally, the front filter segment, the tubular aerosol-forming substrate, one or both of the first hollow tube and the second hollow tube, and the mouth filter segment filter are defined by a wrapper, such as a paper wrapper.

Optionally, the front filter segment has a length of between 2 to 10, 3 to 8, or 4 to 6mm, for example around 5 mm. Optionally, the aerosol-forming substrate has a length of between 5 and 20, 8 and 15, or 10 and 15mm, for example around 12 mm. Optionally, the first hollow tube has a length of between 2 to 20, 5 to 15, or 5 to 10mm, for example around 8 mm. Optionally, the second hollow tube has a length of between 2 to 20, 5 to 15, or 5 to 10mm, for example around 8 mm. Optionally, the mouth filter segment filter has a length of between 5 to 20, 8 to 15, or 10 to 15mm, for example around 12 mm. The length of one or more of the front filter segment, aerosol-forming substrate, first hollow tube, second hollow tube and mouth filter segment filter may extend in the longitudinal direction.

One or more of the front filter segment, aerosol-forming substrate, first hollow tube, second hollow tube, and mouth filter segment filter may be generally cylindrical in shape, such as right cylindrical.

According to one aspect of the present disclosure, an aerosol-generating system is provided.

The system may comprise an aerosol-generating article and an electrically powered aerosol-generating device. The article may be an article as described above, for example an article according to the third aspect.

Optionally, the electrically powered aerosol-generating device is configured to resistively heat the aerosol-generating article in use.

Optionally, the electrically powered aerosol-generating device is configured to inductively heat an aerosol-generating article, such as an aerosol-forming substrate of the aerosol-generating article, in use.

According to the present disclosure there is provided a method of forming a hollow tubular aerosol-forming substrate, such as the substrate for an aerosol-generating article as described above. The method may include forming a slurry comprising one or more or all of thermally conductive particles, an aerosol former, fibers, and a binder. The method may include casting and drying the slurry to form an aerosol-forming substrate, or extruding the slurry to form an aerosol-forming substrate, or casting and drying the slurry to form a precursor such as a sheet of aerosol-forming material and then forming the precursor into an aerosol-forming substrate.

Optionally, the slurry comprises water. Optionally, the slurry comprises 20 to 90, 30 to 90, 40 to 85, 50 to 80, 60 to 80, or 60 to 75 weight percent water.

Optionally, the slurry comprises an acid. Optionally, the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid and levulinic acid.

Optionally, the slurry comprises nicotine.

Optionally, forming the slurry includes forming a first mixture. The first mixture may comprise an aerosol former. The first mixture may comprise fibers. The first mixture may comprise water. The first mixture may comprise an acid. The first mixture may comprise nicotine. Forming the slurry may include forming a second mixture. The second mixture may comprise thermally conductive particles. The second mixture may comprise a binder. Forming the slurry may include adding the second mixture to the first mixture to form a combined mixture.

Thus, forming the slurry may include:

forming a first mixture comprising an aerosol former, fibers, water, optionally an acid, and optionally nicotine;

forming a second mixture comprising thermally conductive particles and a binder;

and adding the second mixture to the first mixture to form a combined mixture.

The combined mixture may then be formed into a slurry, for example, by mixing.

Optionally, forming the first mixture includes providing an aerosol former or a solution comprising an aerosol former and nicotine.

Optionally, forming the first mixture includes adding an acid to the aerosol former or a solution comprising the aerosol former and nicotine to form a first pre-mixture.

Optionally, forming the first mixture comprises adding water to the aerosol former or a solution comprising the aerosol former and nicotine or to the first pre-mixture to form the second pre-mixture.

Optionally, forming the first mixture includes adding fibers to the second premix.

Optionally, forming the second mixture includes mixing thermally conductive particles with a binder.

Optionally, the method, e.g., the step of forming a slurry, includes a first mixing of the combined mixture. Optionally, the first mixing is performed at a first pressure of no more than 500, 400, 300, 250 or 200 millibars. Optionally, the first mixing is performed for between 1 to 10, 2 to 8, or 3 to 6 minutes, for example about 4 minutes.

Optionally, the method, e.g., the step of forming a slurry, includes a second mixing after the first mixing. Optionally, the second mixing is performed at a second pressure that is less than the first pressure. Optionally, the second pressure is no greater than 500, 400, 300, 200, 150 or 100 millibars. Optionally, the second mixing is performed for between 5 to 120, 5 to 80, 5 to 40, or 10 to 30 seconds, for example about 20 seconds.

Optionally, casting the slurry includes casting the slurry onto a flat support, such as a steel flat support.

Optionally, after casting the slurry and before drying the slurry, the method comprises setting the thickness of the slurry, for example, to between 100 and 1200, 200 and 1000, 300 and 900, 500 and 700 micrometers, for example, around 600 micrometers.

Optionally, drying the slurry includes providing a gas stream, such as air, over or through the slurry. Optionally, the gas stream is heated. Optionally, the gas stream is heated to a temperature between 100 and 160, or 120 and 140 degrees celsius. Optionally, the gas flow is provided for between 1 to 10, or 2 to 5 minutes. Optionally, drying the slurry comprises drying the slurry until the slurry has a moisture content of between 1 to 20, 2 to 15, 2 to 10, or 3 to 7 weight percent.

Optionally, drying the slurry forms a precursor for forming an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method comprises cutting a sheet of aerosol-forming material.

The sheet of aerosol-forming material may be formed into an aerosol-forming substrate by rolling the sheet of aerosol-forming substrate into a tube. The walls of the tube are thus formed from a sheet of aerosol-forming material. The tubular shape may be maintained by overlapping a portion of the rolled sheet and fixing the overlapped portion with an adhesive such as a gum. The wall of the tube formed by rolling up the sheet of aerosol-forming material may have a thickness equal to the sheet of aerosol-forming material, i.e. the tube may be formed from a single layer of sheet of aerosol-forming material. However, the walls of the tube may be formed from a multi-layer sheet material that is rolled into the form of a tube. Once rolled and fastened, the tube of aerosol-forming material may be cut into lengths to form tubular sections of aerosol-forming substrate.

As will be appreciated by those of skill in the art upon reading this disclosure, features described herein with respect to one aspect may be applied to any other aspect.

As used herein, the term "aerosol-forming substrate" may refer to a substrate capable of releasing an aerosol or volatile compounds that may form an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate may comprise an aerosol-forming material. The aerosol-forming substrate may be adsorbed, coated, impregnated or otherwise loaded onto the carrier or support. The aerosol-forming substrate may suitably be an aerosol-generating article or a part of a smoking article.

As used herein, the term "thermally conductive particles" may refer to particles having a thermal conductivity of greater than 0.3, preferably 0.5 or more preferably 1W/(mK) at 25 degrees celsius in at least one direction, for example at 25 degrees celsius in all directions. The particles may exhibit anisotropic or isotropic thermal conductivity.

As used herein, the term "expanded graphite" may refer to a graphite-based material or a material having a graphite-like structure. The expanded graphite may have carbon layers (e.g., similar to graphite) with spacing between the carbon layers being greater than the spacing present between the carbon layers in regular graphite. The expanded graphite may have carbon layers with elements or compounds intercalated in the spaces between the carbon layers.

As used herein, the term "particle size" may refer to a single size and may be used to characterize the size of a given particle. The size may be the diameter of a spherical particle occupying the same volume as a given particle. All particle sizes and particle size distributions herein can be obtained using standard laser diffraction techniques. Particle sizes and particle size distributions as described herein can be obtained using commercially available sensors, such as Sympatec HELOS laser diffraction sensors.

As used herein, the term "density" may be used to refer to true density, unless otherwise specified. Thus, without being otherwise specified, the density of a powder or plurality of particles may refer to the true density of the powder or plurality of particles (rather than the bulk density of the powder or plurality of particles, which may vary greatly depending on how the powder or plurality of particles is handled). The measurement of true density can be accomplished using a number of standard methods, which are generally based on archimedes' principle. When used to measure the true density of a powder, the most widely used method requires that the powder be placed in a container of known volume (a gravity bottle) and weighed. The gravity bottle is then filled with a fluid of known density in which the powder is insoluble. The volume of the powder is determined by the difference between the volume as shown in the pycnometer and the volume of liquid added (i.e. the volume of air expelled).

As used herein, the term "aerosol-generating article" may refer to an article capable of generating or releasing an aerosol, for example, when heated.

As used herein, the term "longitudinal" may refer to a direction extending between a downstream or proximal end and an upstream or distal end of a component such as an aerosol-forming substrate or an aerosol-generating article.

As used herein, the term "transverse" may refer to a direction perpendicular to the longitudinal direction.

As used herein, the term "aerosol-generating device" may refer to a device for use with an aerosol-generating article to enable the generation or release of an aerosol.

As used herein, the term "sheet" may refer to a generally planar layered element having a width and length that are substantially greater than its thickness, e.g., at least 2, 3, 5, 10, 20, or 50 times.

As used herein, the term "aerosol former" may refer to any suitable known compound or mixture of compounds that, in use, promotes the formation of an aerosol. The aerosol may be a dense and stable aerosol. The aerosol may be substantially resistant to thermal degradation at the operating temperature of the aerosol-forming substrate or aerosol-generating article.

As used herein, an "aerosol-cooling element" may refer to a component of an aerosol-generating article that is located downstream of an aerosol-forming substrate such that, in use, an aerosol formed from the substrate or from volatile compounds released from the aerosol-forming substrate passes through and is cooled by the aerosol-cooling element prior to inhalation by a user.

As used herein, the term "bar" may refer to a generally cylindrical element, such as a right cylindrical element, having a generally circular, oval, or elliptical cross-section.

As used herein, the term "ventilation level" may refer to the volume ratio of the airflow (ventilation airflow) entering the aerosol-generating article via the ventilation zone to the sum of the aerosol-airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol stream delivered to the consumer.

The invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

Exi an aerosol-generating article for generating an inhalable aerosol, the aerosol-generating article comprising a hollow tubular aerosol-forming substrate, wherein the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former.

Ex1 an aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising a plurality of components 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, wherein the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former.

Ex2 the aerosol-generating article of example Exi or Ex1, wherein each of the plurality of thermally conductive particles has a thermal conductivity greater than 1, 2, 5, 10, 20, 50, 100, 200, 500, or 1000W/mK.

Ex3 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate comprises, on a dry weight basis: between 5 and 95 wt%, e.g. between 10 and 90 wt%, of thermally conductive particles, each of the thermally conductive particles having a thermal conductivity of at least 1W/(mK) in at least one direction at 25 degrees celsius.

Ex4 an aerosol-generating article according to example Ex3, wherein the aerosol-forming substrate further comprises between 7 and 60 wt% of an aerosol-forming agent; between 2 and 20 weight percent fiber; and between 2 and 10 wt% of a binder.

Ex5 an aerosol-generating article according to example Ex3 or Ex4, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12W/(mK), e.g. at least 0.14W/(mK), e.g. at least 0.22W/(mK), in at least one direction at 25 degrees celsius.

An aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate comprises, on a dry weight basis: between 10 and 90 wt% thermally conductive particles; between 7 and 60 wt% aerosol former; between 2 and 20 weight percent fiber; and between 2 and 10 wt% of a binder, wherein each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

An aerosol-generating article according to any preceding example, wherein each thermally conductive particle of the plurality of thermally conductive particles has a thermal conductivity of at least 0.3, 0.5, 1, 2, 5 or 10W/(mK) in at least one direction, for example, when measured at 25 degrees celsius.

Ex8 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles comprise carbon, for example at least 10, 30, 50, 70, 90, 95, 98 or 99 wt% carbon.

An aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles are graphite particles, or some or all of the thermally conductive particles are expanded graphite particles, or some of the thermally conductive particles are graphite particles and some of the thermally conductive particles are expanded graphite particles.

Ex10 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles are diamond particles, such as synthetic diamond particles.

Ex11 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles are graphene particles.

Ex12 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles are carbon nanotubes.

Ex13 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles are charcoal particles.

Ex14 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles comprise a metal.

Ex15 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles comprise one or both of copper and aluminum.

Ex16 an aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles comprise an alloy.

An aerosol-generating article according to any preceding example, wherein some or all of the thermally conductive particles comprise an intermetallic compound.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D10 of particle sizes, wherein the number D10 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D10 of particle sizes, wherein the number D10 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D50 of particle sizes, wherein the number D50 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D50 of particle sizes, wherein the number D50 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D90 of particle sizes, wherein the number D90 of particle sizes is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D90 of particle sizes, wherein the number D90 of particle sizes is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D10 particle size, wherein the volume D10 particle size is no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D50 particle size, wherein the volume D50 particle size is not greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5 or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a volume D90 particle size, wherein the volume D90 particle size is not greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5 or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution having a number D10 particle size, a number D90 particle size, a volume D10 particle size, and a volume D90 particle size, wherein: the number D90 particle size is not greater than 50, 40, 30, 20, 10 or 5 times the number D10 particle size, or the volume D10 particle size is not greater than 50, 40, 30, 20, 10 or 5 times the volume D10 particle size, or both the number D90 particle size is not greater than 50, 40, 30, 20, 10 or 5 times the number D10 particle size and the volume D10 particle size is not greater than 50, 40, 30, 20, 10 or 5 times the volume D10 particle size.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution and one or both of a number D10 particle size and a volume D10 particle size is between 1 and 20 microns.

An aerosol-generating article according to any preceding example, wherein the thermally conductive particles have a particle size distribution wherein one or both of the number D90 particle size and the volume D90 particle size is between 50 and 300 microns or between 50 and 200 microns.

An aerosol-generating article according to any preceding example, wherein each of the thermally conductive particles has a particle size of at least 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, or 500 microns.

An aerosol-generating article according to any preceding example, wherein each of the thermally conductive particles has a particle size of no greater than 1,000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

An aerosol-generating article according to any preceding example, wherein each of the thermally conductive particles has three mutually perpendicular dimensions, a largest dimension of the three dimensions being no more than 10, 8, 5, 3 or 2 times larger than a smallest dimension of the three dimensions and a second largest dimension of the three dimensions.

An aerosol-generating article according to any preceding example, wherein each of the thermally conductive particles is substantially spherical.

Ex37 an aerosol-generating article according to any preceding example, wherein the thermally conductive particles comprise at least 10, 20, 50, 100, 200, 500, or 1000 particles.

An aerosol-generating article according to any preceding example, wherein the matrix comprises at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 wt% thermally conductive particles on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20 or 15 wt% thermally conductive particles on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises between 10 to 90, 20 to 90, 30 to 90, 40 to 90, 50 to 90, 60 to 90, 70 to 90, 80 to 90, 10 to 80, 20 to 80, 30 to 80, 40 to 80, 50 to 80, 60 to 80, 70 to 80, 10 to 70, 20 to 70, 30 to 70, 40 to 70, 50 to 70, 60 to 70, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 10 to 40, 20 to 40, 30 to 40, 10 to 30, 20 to 30, or 10 to 20% by weight of thermally conductive particles on a dry weight basis.

Ex41 an aerosol-generating article according to any preceding example, wherein the matrix comprises at least 10, 15, 20, 25, 30, 35, 40, 45, 50 or 55 wt% aerosol former on a dry weight basis.

Ex42 an aerosol-generating article according to any preceding example, wherein the matrix comprises no more than 55, 50, 45, 40, 35, 30, 25, 20 or 15 wt% aerosol former on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises between 7 to 60, 10 to 60, 20 to 60, 30 to 60, 40 to 60, 50 to 60, 7 to 50, 10 to 50, 20 to 50, 30 to 50, 40 to 50, 7 to 40, 10 to 40, 20 to 40, 30 to 40, 7 to 30, 10 to 30, 20 to 30, 7 to 20, 10 to 20, or 7 to 10% by weight of aerosol-forming agent, particularly preferably between 15 to 25% by weight of aerosol-forming agent, on a dry weight basis.

Ex44 an aerosol-generating article according to any preceding example, wherein the aerosol-former comprises or consists of one or more of the following: polyhydric alcohols such as propylene glycol, polyethylene glycol, triethylene glycol, 1, 3-butanediol, and glycerol; esters of polyhydric alcohols, such as glycerol mono-, di-or triacetate; and aliphatic esters of monocarboxylic, dicarboxylic or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Ex45 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate comprises one or both of glycerol and glycerin.

Ex46 an aerosol-generating article according to any preceding example, wherein the matrix comprises at least 2, 4, 6, 8, 10, 12, 14, 16 or 18 wt% fibres on a dry weight basis.

Ex47 an aerosol-generating article according to any preceding example, wherein the matrix comprises no more than 20, 18, 16, 14, 12, 10, 8, 6 or 4 wt% fibres on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises, on a dry weight basis, 4 to 20, 6 to 20, 8 to 20, 10 to 20, 12 to 20, 14 to 20, 16 to 20, 18 to 20, 2 to 18, 4 to 18, 6 to 18, 8 to 18, 10 to 18, 12 to 18, 14 to 18, 16 to 18, 2 to 16, 4 to 16, 6 to 16, 8 to 16, 10 to 16, 12 to 16, 14 to 16, 2 to 14, 4 to 14, 6 to 14, 8 to 14, 10 to 14, 12 to 14, 2 to 12, 4 to 12, 6 to 12, 8 to 12, 10 to 12, 2 to 10, 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4

Between 8, 6 and 8, 2 and 6, 4 and 6, or 2 and 4% by weight of fibers, particularly preferably between 2 and 10% by weight of fibers.

Ex49 an aerosol-generating article according to any preceding example, wherein the fibers are cellulosic fibers.

An aerosol-generating article according to any preceding example, wherein each fiber has three mutually perpendicular dimensions, the largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10 or 20 times larger than the smallest dimension of the three dimensions.

An aerosol-generating article according to any preceding example, wherein each fiber has three mutually perpendicular dimensions, the largest dimension of the three dimensions being at least 1.5, 2, 3, 5, 10 or 20 times larger than the second largest dimension of the three dimensions.

An aerosol-generating article according to any preceding example, wherein the matrix comprises at least 4, 6 or 8 wt% binder on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises no more than 8, 6 or 4 wt% binder on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises between 4 to 10, 6 to 10, 8 to 10, 2 to 8, 4 to 8, 6 to 8, 2 to 6, 4 to 6, 2 to 4% by weight binder, particularly preferably between 2 to 10% by weight binder on a dry weight basis.

Ex55 an aerosol-generating article according to any preceding example, wherein the binder comprises or consists of one or both of carboxymethyl cellulose or hydroxypropyl cellulose.

Ex56 an aerosol-generating article according to any preceding example, wherein the binder comprises or consists of one or more gums such as guar gum.

Ex57 an aerosol-generating article according to any preceding example, wherein the thermally conductive particles are substantially uniformly distributed throughout the aerosol-forming substrate.

An aerosol-generating article according to any preceding example, wherein the aerosol-forming agent is substantially uniformly distributed throughout the aerosol-forming substrate.

An aerosol-generating article according to any preceding example, wherein the fibres are substantially uniformly distributed throughout the aerosol-forming substrate.

Ex60 an aerosol-generating article according to any preceding example, wherein the binder is substantially uniformly distributed throughout the aerosol-forming substrate.

An aerosol-generating article according to any preceding example, wherein the substrate comprises nicotine.

Ex62 an aerosol-generating article according to example Ex61, wherein the substrate comprises at least 0.01, 1, 2, 3, or 4 wt% nicotine on a dry weight basis.

Ex63 an aerosol-generating article according to any of examples Ex61 to Ex62, wherein the substrate comprises no more than 5, 4, 3, 2 or 1 wt% nicotine on a dry weight basis.

An aerosol-generating article according to any preceding example, wherein the matrix comprises between 0.01 to 5, 1 to 5, 2 to 5, 3 to 5, 4 to 5, 0.01 to 4, 1 to 4, 2 to 4, 3 to 4, 0.01 to 3, 1 to 3, 2 to 3, 0.01 to 2, 1 to 2, 0.01 to 1% by weight nicotine, particularly preferably between 0.5 to 4% by weight nicotine on a dry weight basis.

Ex65 an aerosol-generating article according to any of examples Ex61 to Ex63, wherein the nicotine is substantially uniformly distributed throughout the aerosol-forming substrate.

An aerosol-generating article according to any preceding example, wherein the matrix comprises an acid.

Ex67 an aerosol-generating article according to example Ex66, wherein the matrix comprises at least 0.01, 1, or 2 wt% acid on a dry weight basis.

Ex68 an aerosol-generating article according to any of examples Ex66 to Ex67, wherein the matrix comprises no more than 3, 2 or 1 wt% acid on a dry weight basis.

An aerosol-generating article according to any of examples Ex66 to Ex68, wherein the matrix comprises between 0.01 and 3, 1 and 3, 2 and 3, 0.01 and 2, 1 and 2, 0.01 and 1 wt% acid, particularly preferably between 0.5 and 5 wt% acid on a dry weight basis.

Ex70 an aerosol-generating article according to any of examples Ex66 to Ex69, wherein the acid comprises or consists of one or more of fumaric acid, lactic acid, benzoic acid, and levulinic acid.

Ex71 an aerosol-generating article according to any of examples Ex66 to Ex70, wherein the acid is substantially uniformly distributed throughout the aerosol-forming substrate.

Ex72 an aerosol-generating article according to any preceding example, wherein the matrix comprises at least one plant-derived material.

Ex73 an aerosol-generating article according to example Ex72, wherein the matrix comprises at least 0.01, 1, 2, 5, 10, or 15 wt% of the at least one plant-derived material on a dry weight basis.

An aerosol-generating article according to any of examples Ex72 to Ex73, wherein the matrix comprises not more than 20, 15, 10, 5, 2 or 1 wt% of the at least one plant-derived material on a dry weight basis.

The aerosol-generating article according to any one of examples Ex72 to Ex74, wherein the matrix comprises between 0.01 and 20, 1 and 20, 2 and 20, 5 and 20, 10 and 20, 15 and 20, 0.01 and 15, 1 and 15, 2 and 15, 5 and 15, 10 and 15, 0.01 and 10, 1 and 10, 2 and 10, 5 and 10, 0.01 and 5, 1 and 5, 2 and 5, 0.01 and 2, 1 and 2, 0.01 and 1% by weight of the at least one plant-derived material, particularly preferably between 1 and 15% by weight of the at least one plant-derived material, on a dry weight basis.

The aerosol-generating article according to any one of examples Ex72 to Ex75, wherein the at least one plant-derived material comprises or consists of one or both of clove and rosemary.

An aerosol-generating article according to any of examples Ex72 to Ex76, wherein the at least one plant-derived material is substantially uniformly distributed throughout the aerosol-forming substrate.

An aerosol-generating article according to any preceding example, wherein the matrix comprises at least one flavour.

Ex79 an aerosol-generating article according to example Ex78, wherein the matrix comprises at least 0.1, 1, 2, or 5 wt% of the at least one flavoring agent on a dry weight basis.

Ex80 an aerosol-generating article according to any of examples Ex78 to Ex79, wherein the matrix comprises not more than 10, 5, 2 or 1 wt% of the at least one flavouring agent on a dry weight basis.

The aerosol-generating article according to any one of examples Ex78 to Ex80, wherein the matrix comprises between 0.1 and 10, 1 and 10, 2 and 10, 5 and 10, 0.1 and 5, 1 and 5, 2 and 5, 0.1 and 2, 1 and 2, 0.1 and 1 wt% of the at least one flavour agent, particularly preferably between 0.1 and 5 wt% of the at least one flavour agent on a dry weight basis.

Ex82 the aerosol-generating article according to any of examples Ex78 to Ex81, wherein the at least one flavoring agent is present as a coating, e.g. a coating on one or more other components of the aerosol-forming substrate.

Ex83 an aerosol-generating article according to any of examples Ex78 to Ex82, wherein the at least one flavoring agent is substantially uniformly distributed throughout the aerosol-forming substrate.

Ex84 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate comprises one or more organic materials such as tobacco.

Ex85 the aerosol-generating article of any preceding example, wherein the organic material comprises one or more of herb leaf, tobacco leaf rib segment, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco.

Ex86 an aerosol-generating article according to any preceding example, wherein the organic material is substantially uniformly distributed throughout the aerosol-forming substrate.

Ex87 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate is a smokeless tobacco aerosol-forming substrate, e.g., wherein the aerosol-forming substrate does not comprise tobacco.

Ex88 an aerosol-generating article according to any preceding example, wherein some or each of the thermally conductive particles comprises and/or is formed from a susceptor material, such as a carbon susceptor material.

An aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.15, 0.2, 0.22, 0.3, 0.4, 0.5, 0.75, 1, 1.25 or 1.5W/(mK) at 25 degrees celsius in at least one direction or in all directions.

Ex90 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a density of less than 1500, 1050, 1000, 950, 900, 850, 800, 750, 700, or 650kg/m 3.

Ex91 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a weight of 500 to 900 or 600 to 800kg/m ³ Density of the two.

Ex92 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a moisture content of between 1 to 20, or 3 to 15 wt%.

An aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate comprises between 1 and 20, or 3 and 15 wt% water.

The aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a concentration of at least 0.1, 0.2, 0.3 or 0.5g/m ³ Is a density of (3).

Ex95 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a weight of no greater than 2, 1.5, 1.2, or 1g/m ³ Is a density of (3).

The aerosol-generating article of any preceding example, wherein the aerosol-forming substrate has a weight of 0.1 to 2, 0.2 to 2, 0.3 to 1.5, or 0.3 to 1.2g/m ³ Density of the two.

An aerosol-generating article according to any preceding example, wherein the substrate is in the form of a tube having a width in a radial dimension and a length in a longitudinal dimension, wherein the length is between 5mm and 100mm, such as between 6mm and 80mm, such as between 7mm and 60mm, such as between 8mm and 55mm, such as between 9mm and 50mm, such as between 10mm and 45mm, such as between 11mm and 35mm, such as between 12mm and 25 mm.

An aerosol-generating article according to any preceding example, wherein the substrate is in the form of a tube having a width in a radial dimension and a length in a longitudinal dimension, wherein the width is defined by an outer diameter of the tube, the outer diameter being between 3mm and 20mm, such as between 4mm and 12mm, such as between 4.5mm and 10mm, such as between 5mm and 9mm, such as between 6mm and 8mm, such as between 6.5mm and 7.5mm, such as about 7mm.

An aerosol-generating article according to any preceding example, wherein the substrate is in the form of a tube having an outer diameter and an inner diameter, the inner diameter being between 2.5mm and 19mm, such as between 3.5mm and 11.5mm, such as between 4mm and 9mm, such as between 4.5mm and 8.5mm, such as between 5.5mm and 7.5mm, such as between 6.9mm and 7.3mm, such as about 7mm.

An aerosol-generating article according to any preceding example, wherein the substrate is in the form of a tube having a length, an outer diameter and an inner diameter, the wall thickness of the tube being defined by the difference between the outer diameter and the inner diameter, wherein the wall thickness is between 100 microns and 5mm, such as between 150 microns and 3mm, such as between 200 microns and 2mm, such as between 250 microns and 1.5mm, such as between 300 microns and 1mm, such as between 350 microns and 500 microns.

Ex101 an aerosol-generating article according to any preceding example, wherein the substrate is in the form of a tube and the tube is a rolled sheet of aerosol-forming material, such as a rolled sheet of homogenized tobacco material, such as a rolled sheet of cast leaf tobacco, or such as a rolled sheet of smokeless aerosol-forming material.

The aerosol-generating article according to any one of examples Exi to Ex100, wherein the substrate is in the form of a tube and the tube is a tube of extruded aerosol-forming material, such as a tube of extruded homogenized tobacco material or such as a tube of extruded smokeless aerosol-forming material.

An aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises a front filter segment, for example wherein the front filter segment has a length of between 2mm and 10mm, 3mm and 8mm, or 4mm and 6mm, for example around 5 mm.

Ex104 an aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises a first hollow support tube, e.g. a first hollow acetate tube, e.g. wherein the first hollow support tube is located downstream of an aerosol-forming substrate within the aerosol-generating article.

Ex105 an aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises a second hollow support tube, e.g. a second hollow acetate tube, e.g. wherein the second hollow support tube is located downstream of the aerosol-forming substrate within the aerosol-generating article.

Ex106 an aerosol-generating article according to example Ex105, wherein the second hollow support tube comprises one or more ventilation holes.

Ex107 an aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises an oral filter segment filter.

Ex108 an aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises a wrapper, such as a paper wrapper, for example wherein components of the aerosol-generating article comprising the aerosol-forming substrate are assembled within the wrapper.

Ex109 an aerosol-generating article according to any preceding example, wherein the aerosol-generating article comprises a front filter segment, an aerosol-forming substrate disposed downstream of the front filter segment, a first hollow support tube disposed downstream of the aerosol-forming substrate, a second hollow support tube disposed downstream of the first hollow support tube, and a mouth filter segment filter disposed downstream of the second hollow tube, preferably wherein the front filter segment, the aerosol-forming substrate, the first hollow support tube, the second hollow support tube, and the mouth filter segment filter are defined by a wrapper (e.g., a paper wrapper).

Ex110 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a length of between 5 mm and 30 mm.

Ex111 an aerosol-generating article according to any preceding example, wherein the aerosol-forming substrate has a length of between 5 mm and 16 mm.

An aerosol-generating article according to any preceding example, wherein the wall thickness of the aerosol-forming substrate is between 5% and 40% of the outer diameter of the aerosol-forming substrate.

Ex113 a method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example an aerosol-generating article as defined by any of examples Exi to Ex112, the method comprising:

forming a slurry comprising thermally conductive particles, an aerosol former, fibers, and a binder;

casting the slurry into the shape of a hollow tubular aerosol-forming substrate, and

drying the cast slurry to form a hollow tubular aerosol-forming substrate.

Ex114 a method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example an aerosol-generating article as defined by any of examples Exi to Ex112, the method comprising:

extruding the slurry into the shape of a hollow tubular aerosol-forming substrate, and

the extruded slurry is dried into a hollow tube.

Ex115 the method according to example Ex114, further comprising the step of cutting the hollow tube to form a hollow tubular aerosol-forming substrate.

Ex116 a method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example an aerosol-generating article as defined by any of examples Exi to Ex112, the method comprising:

casting and drying the slurry to form a sheet of aerosol-forming material, and

the sheet is formed into a hollow tube.

Ex117 the method according to example Ex116, further comprising the step of cutting the hollow tube to form a hollow tubular aerosol-forming substrate.

Ex118 the method according to example Ex116 or Ex117, wherein the step of forming the sheet into a hollow tube comprises the steps of rolling the sheet into a tubular shape and applying an adhesive to overlapping portions of the rolled sheet to hold the rolled sheet in the tubular shape.

Ex119 the method according to any one of examples Ex113 to Ex118, wherein the slurry comprises water.

Ex120 the method according to any one of examples Ex113 to Ex119, wherein the slurry comprises 40 to 90, 40 to 85, 50 to 80, 60 to 75 weight percent water.

Ex121 the method according to any one of examples Ex113 to Ex120, wherein the slurry comprises an acid such as fumaric acid.

Ex122 the method according to any one of examples Ex113 to Ex121, wherein the slurry comprises nicotine.

Ex123 the method of any one of examples Ex113 to Ex122, wherein forming the slurry comprises:

forming a first mixture comprising:

an aerosol former;

a fiber;

water;

optionally, the acid; and

optionally, the nicotine is used for producing a medicament,

forming a second mixture comprising:

the thermally conductive particles; and

the presence of the binder is not limited to a specific type,

and adding the second mixture to the first mixture to form a combined mixture.

Ex124 the method of example Ex123, wherein forming the first mixture comprises providing an aerosol former or a solution comprising an aerosol former and nicotine.

Ex125 the method of example Ex124, wherein forming the first mixture comprises adding an acid to the aerosol former or a solution comprising the aerosol former and nicotine to form a first pre-mixture.

Ex126 the method of any of examples Ex123 to Ex125, wherein forming the first mixture comprises adding water to the aerosol former or a solution comprising the aerosol former and nicotine or to the first pre-mixture to form the second pre-mixture.

Ex127 the method according to example Ex126, wherein forming the first mixture comprises adding fibers to the second pre-mix.

Ex128 the method of any of examples Ex126 to Ex127, wherein forming the second mixture comprises mixing thermally conductive particles with a binder.

Ex129 the method of any of examples Ex126 to Ex128, wherein the method comprises a first mixing of the combined mixture.

Ex130. the method according to example Ex129, wherein the first mixing is performed at a first pressure of no greater than 500, 400, 300, 250, or 200 millibars.

Ex131 the method according to example Ex129 or Ex130, wherein said first mixing is performed for between 1 to 10, 2 to 8, or 3 to 6 minutes, e.g. about 4 minutes.

Ex132 the method of any one of examples Ex129 to Ex131, wherein the method comprises performing a second mixing after mixing the first mixing.

Ex133 the method of example Ex132, wherein the second mixing is performed at a second pressure that is less than the first pressure.

Ex134 the method according to example Ex133, wherein the second pressure is no greater than 500, 400, 300, 200, 150, or 100 millibars.

Ex135 the method according to examples Ex132 or Ex133 or Ex134, wherein said second mixing is performed for between 5 to 120, 5 to 80, 5 to 40, or 10 to 30 seconds, e.g. around 20 seconds.

Ex136 the method according to any of examples Ex116 to Ex135, wherein casting the slurry comprises casting the slurry onto a flat support, such as a steel flat support.

Ex137 the method according to any one of examples Ex113 to Ex136, wherein after casting the slurry and before drying the slurry, the method comprises setting the thickness of the slurry, e.g. setting the thickness of the slurry to between 100 and 1,000, 200 to 900, 300 to 800, 500 to 700 micrometers, e.g. around 600 micrometers.

Ex138 the method of any one of examples Ex113 to Ex137, wherein drying the slurry comprises providing a gas stream, such as air, over or through the slurry.

Ex139 the method according to example Ex138, wherein the gas stream is heated.

Ex140 the method according to example Ex139, wherein the gas stream is heated to a temperature between 100 and 160, or 120 and 140 degrees Celsius.

Ex141. the method according to any of examples Ex138 to Ex140, wherein the gas flow is provided for between 1 to 10, or 2 to 5 minutes.

Ex142 the method of any of examples Ex113 to Ex141, wherein drying the slurry comprises drying the slurry until the slurry has a moisture content of between 1 to 20, 2 to 15, 2 to 10, or 3 to 7 weight percent.

Ex143 the method according to any one of examples Ex113 to Ex142, wherein the dried slurry forms a precursor for forming an aerosol-forming substrate, the precursor being a sheet of aerosol-forming material.

Ex144 an aerosol-generating system comprising an aerosol-generating article according to any of examples Exi to Ex112 and an electric aerosol-generating device.

Ex145 the aerosol-generating system of example Ex144, wherein the motorized aerosol-generating device is configured to resistively heat the aerosol-generating article in use.

An aerosol-generating system according to any of examples Ex144 to Ex145, wherein the electrically powered aerosol-generating device is configured to inductively heat an aerosol-generating article, such as an aerosol-forming substrate of an aerosol-generating article, in use.

Several examples will now be further described with reference to the accompanying drawings, in which:

fig. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article;

Fig. 2 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating system comprising the article of fig. 1;

fig. 3 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system comprising the article of fig. 1; and is also provided with

Fig. 4 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating system comprising the article of fig. 1.

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 millimeters and a diameter of about 7.2 mm.

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

The front filter segment 46, also referred to as an upstream element, is positioned immediately upstream of the tubular aerosol-forming substrate 12. The front filter segment 46 is provided in the form of a cylindrical filter segment of cellulose acetate. The front filter segment 46 has a diameter of about 7.2mm and a length of about 5 mm. The RTD of the front filter segment 46 is about 30 mm H ₂ O。

The tubular section of the aerosol-forming substrate 12 has an outer diameter of about 7.2mm, an inner diameter of about 6.8 mm and a length of about 12 mm. The aerosol-forming substrate 12 is formed from a sheet of rolled 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 between 150 degrees celsius and 350 degrees celsius. Some specific examples of suitable aerosol-forming substrate compositions are provided below.

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

The mouthpiece element 42 is provided in the form of a cylindrical filter segment of low density cellulose acetate. The mouthpiece element 42 has a length of about 12 millimeters and an outer diameter of about 7.2 mm. The RTD of the mouthpiece element 42 is about 12 mm H ₂ O。

It should be clear that the configuration of the aerosol-generating article 10 of fig. 1 is intended to be used as an example only.

The thermally enhanced tubular aerosol-forming substrate 12 may be used, for example, in longer (e.g., 80mm long) and thinner (e.g., 4.5mm diameter) aerosol-generating articles.

In a specific embodiment of the aerosol-generating article as illustrated in fig. 1, the tubular section 12 of the aerosol-forming substrate comprises about 76.1% by weight of thermally conductive particles 44 on a dry weight basis. In this embodiment, the thermally conductive particles 44 are Graphite particles, especially FP 99,5 (purity > 99.5%) Graphite particles AMG Graphite GK from Graphit kropfmull GmbH, but other particles or particle mixtures may be used. Each thermally conductive particle has a thermal conductivity of around 6W/(mK) in at least one direction at 25 degrees celsius.

The tubular aerosol-forming substrate 12 comprises about 17.7% by weight on a dry weight basis of aerosol-forming agent. In this embodiment, the aerosol former is glycerol, especially ICOF european food grade (purity > 99.5%) glycerol.

The tubular aerosol-forming substrate 12 comprises about 3.9% by weight fibres on a dry weight basis. In this embodiment, the fibers are cellulosic fibers, particularly Birch cellulosic fibers from Stora Enso OYJ.

The tubular aerosol-forming substrate 12 comprises about 2.3% by weight binder on a dry weight basis. In this embodiment, the binder is guar gum, especially guar gum from Gumix International inc.

The tubular aerosol-forming substrate comprises about 10 wt% water when measured at 25 degrees celsius.

In other embodiments, the tubular aerosol-forming substrate 12 further comprises one or more of nicotine, an acid (e.g., fumaric acid), a plant-derived material (e.g., clove or rosemary), and a flavoring agent.

The tubular aerosol-forming substrate 12 has a thermal conductivity of at least 0.1W/(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, 1.5W/(mK) or greater in at least one direction at 25 degrees celsius.

Each of the thermally conductive particles 44 is generally spherically shaped. The thermally conductive particles 44 are substantially uniformly distributed throughout the aerosol-forming substrate. The particle size distribution has a volume D10 particle size of about 6 microns, a volume D50 particle size of about 20 microns, and a volume D90 particle size of about 56 microns. Each of the thermally conductive particles 44 has a particle size of greater than about 1 micron and less than about 300 microns.

The thermally conductive particles 44 have a density of around 2200 kg/cubic meter. The aerosol-forming substrate has a density of around 800 kg/cubic meter.

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

The slurry is formed using a laboratory disperser capable of mixing a viscous liquid, dispersing the powder in the liquid, and removing gas from the mixture (e.g., by applying a vacuum or other suitable low pressure). In this embodiment, a laboratory disperser commercially available from PC Laborsystem was used.

To form a slurry, a first mixture was formed by adding about 7.11 grams of aerosol former, then about 157.5 grams of water, then about 1.57 grams of fibers to a laboratory disperser. These first ingredients are then mixed at 600-700rpm for 5 minutes at 25 degrees celsius to ensure a uniform mixture is formed and the fibers are hydrated. Then, a second mixture was 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 will avoid the formation of lumps in the laboratory dispersion. The second mixture is then added to the first mixture to form a combined mixture. The combined mixture was then mixed at 5000rpm for 4 minutes at 25 degrees celsius and a first reduced pressure of around 200 millibars. This reduced pressure can help ensure that the thermally conductive particles are uniformly dispersed in the mixture and that there is little entrapped air and lumps in the combined mixture. The combined mixture was then mixed at 5000rpm for 20 seconds at 25 degrees celsius and a second reduced pressure of around 100 millibars. This second reduced pressure may help to remove any remaining bubbles. This forms a slurry for casting.

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

The slurry was cast onto a flat support and the gap between the coma blade and the flat support was set to 0.6 mm. This ensures that the thickness of the slurry does not exceed 0.6 mm at any given point.

The slurry is then dried with hot air at a temperature between 120 and 140 degrees celsius for between 2 and 5 minutes. After this drying, a sheet of aerosol-forming substrate is formed. The sheet has a thickness of about 300 microns, a grammage of about 250 grams per square meter and a density of about 0.79 kilograms per cubic meter.

The sheet is then rolled to form a tube. An adhesive was applied to the overlapped portion of the rolled sheet to fix the sheet in the form of a tube, and then the tube was cut into a length of 12mm to be used as the tubular aerosol-forming substrate 12.

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 packaging the components in the wrapper 70.

Other embodiments may have the same structure as described above, but with a different composition of aerosol-forming substrate. For example, in yet another embodiment, the aerosol-forming material comprises a tube of thermally enhanced homogenized tobacco comprising thermally conductive particles 44. The thermally conductive particles 44 are carbon particles, particularly 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 average particle size of about 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 cubic meter. The aerosol-forming substrate comprising the aerosol-forming material and thermally conductive particles 44 has a combined density of around 760 kg/cubic meter. The expanded graphite particles comprise about 5% by weight of the aerosol-forming substrate.

The tube 12 of aerosol-forming substrate is formed by a process comprising the steps of:

premixing the binder guar gum with an aerosol former glycerol to form a first premix;

premixing the finely divided tobacco material with a powder consisting of expanded graphite particles 44 and having a bulk density of around 0.065 g/cc to form a second premix;

Mixing the first and second premixes with water to form a slurry;

homogenizing the slurry using a high shear mixer;

casting the slurry onto a conveyor belt;

controlling the thickness of the slurry and drying the slurry to form a sheet of aerosol-forming substrate; and

rolling a sheet of aerosol-forming substrate into a tube and cutting the tube to form tubular sections of aerosol-forming substrate.

An aerosol-forming substrate formed with a composition comprising conductive particles according to the invention exhibits improved aerosol delivery compared to a reference substrate without thermally conductive particles.

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.

The aerosol-generating device 102 includes 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 heater blade 108, and the suction detection mechanism.

The aerosol-generating device 102 further comprises a housing 110 defining a generally cylindrical cavity for receiving a portion of the article 10. The heating blades 108 are centrally located within the cavity and extend longitudinally from the bottom of the cavity.

In this embodiment, the heater blade 108 includes a substrate and a resistive track on the substrate. The battery 104 is coupled to the heating blade 108 to enable current to pass through the resistive track and heat the resistive track and the heating blade 108 to an operating temperature.

In use, a user inserts the article 10 into the cavity such that the heating blade 108 penetrates the upstream element 46 and extends into the internal bore or cavity of the tubular 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 bore of the tubular aerosol-forming substrate.

The user then draws on the downstream end of the article 10. This causes air to flow through the air inlet (not shown) of the device 102 and then through the article 10, from the upstream end 18 to the downstream end 20, and into the mouth of the user.

The user draws air over the article 10 causing air to flow through the air inlet of the device. The suction detection mechanism detects that the air flow rate through the air inlet has increased above a non-zero threshold flow rate. The suction detection mechanism accordingly sends a signal to the controller 106. The controller 106 then controls the battery 104 to pass current through the resistive track and heat the heater blade 108. This heats the tubular aerosol-forming substrate.

The thermally conductive particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. Thus, these particles may act as local hot spots and provide a more uniform temperature throughout the aerosol-forming substrate, particularly in the radial direction from the heating blade 108, where there would be a significant temperature gradient if a prior art substrate were used. Furthermore, since the aerosol-forming substrate is in the form of a tube, the temperature is relatively quickly equalized between the inner surface of the tube and the outer surface of the tube. The combination of the tubular structure of the aerosol-forming substrate and the presence of thermally conductive particles in the aerosol-forming substrate allows a larger proportion of the aerosol-forming substrate to reach a sufficiently high temperature quickly to release volatile compounds and thus allows for a higher efficiency of use of the aerosol-forming substrate.

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 toward the downstream end 20 of the article 10. The compounds cool and condense as they pass through the paperboard tube 34 to form an aerosol. The aerosol then passes through the mouthpiece element 42, which may filter out unwanted particles entrained in the air stream, and into the mouth of the user.

When the user stops inhaling on the article 10, the air flow rate through the air inlet of the device is reduced to less than the non-zero threshold flow rate. This is detected by the suction detection mechanism. The suction detection mechanism accordingly sends a signal to the controller 106. The controller 106 then controls the battery 104 to reduce the current through the resistive track to zero.

After multiple puffs on the article 10, the user may choose to replace the article 10 with a new article.

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.

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

The aerosol-generating device 302 further comprises a housing 310 defining a generally cylindrical cavity for receiving a portion of the article 10. An external heater 208 is located on the inner surface of the chamber.

The use of the system is similar to that described above with respect to the system of fig. 2, except that the tubular aerosol-forming substrate 12 is heated from the outside rather than by a heater located in the interior portion of the aerosol-forming substrate.

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.

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 suction detection mechanism.

The aerosol-generating device 402 further comprises a housing 410 defining a generally cylindrical cavity for receiving a portion of the article 10. The inductor coil 408 surrounds the cavity in a spiral fashion.

The battery 404 is coupled to the inductor coil 408 to enable an alternating current to pass through the inductor coil 408.

In use, a user inserts the article 10 into the cavity. Fig. 4 shows the article 10 inserted into a cavity of a device 402. The airflow is detected and the device is actuated as described above with respect to the system of fig. 1. When aspiration is detected, the controller 406 controls the battery 404 to pass 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 material of the particles 44 (e.g., graphite or expanded graphite) is a susceptor material. Thus, the fluctuating electromagnetic field induces eddy currents in the particles 44. This causes the particles 44 to heat up, thereby also heating the aerosol-forming material of the aerosol-forming substrate.

For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, amounts, percentages, and so forth, are to be understood as being modified in all instances by the term "about". Additionally, all ranges include the disclosed maximum and minimum points, and include any intervening ranges therein, which may or may not be specifically enumerated herein. Thus, in this context, the number a is understood to be a±10% a. In this context, the number a may be considered to include values within a general standard error for the measurement of the property of the modification of the number a. In some cases, as used in the appended claims, the number a may deviate from the percentages recited above, provided that the amount of deviation a does not materially affect the basic and novel characteristics of the claimed invention. Additionally, all ranges include the disclosed maximum and minimum points, and include any intervening ranges therein, which may or may not be specifically enumerated herein.

Claims

1. An aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising a plurality of components 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, wherein the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former.

2. An aerosol-generating article according to claim 1, wherein the aerosol-forming substrate comprises, on a dry weight basis: between 5 and 95 wt%, e.g. between 10 and 90 wt%, of thermally conductive particles, each of the thermally conductive particles having a thermal conductivity of at least 1W/(mK) in at least one direction at 25 degrees celsius.

3. An aerosol-generating article according to claim 1 or 2, wherein the aerosol-forming substrate has a thermal conductivity of at least 0.12W/(mK) in at least one direction at 25 degrees celsius.

4. An aerosol-generating article according to any preceding claim, wherein each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal and diamond.

5. An aerosol-generating article according to any preceding claim, wherein the aerosol-forming substrate comprises, on a dry weight basis: between 10 and 90 wt% thermally conductive particles; between 7 and 60 wt% aerosol former; between 2 and 20 weight percent fiber; and between 2 and 10 wt% of a binder, wherein each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

6. An aerosol-generating article according to any preceding claim, wherein the thermally conductive particles are substantially uniformly distributed throughout the aerosol-forming substrate.

7. An aerosol-generating article according to any preceding claim, wherein the aerosol-forming substrate comprises one or more organic materials such as tobacco.

8. An aerosol-generating article according to any one of claims 1 to 6, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

9. An aerosol-generating article according to any preceding claim, wherein the aerosol-forming substrate is in the form of a tube having an outer diameter, an inner diameter and a length, wherein the length of the tube is between 5mm and 100mm, the outer diameter is between 3mm and 20mm, and the inner diameter is between 2.5mm and 19.5 mm.

10. An aerosol-generating article according to claim 9, wherein the length of the tube is between 8mm and 25mm, the outer diameter of the tube is between 6mm and 8mm, and the inner diameter of the tube is between 5mm and 7.9 mm.

11. An aerosol-generating article according to any preceding claim, wherein the hollow tubular section is a rolled sheet of aerosol-forming material, such as a rolled sheet of homogenized tobacco material or a rolled sheet of smokeless aerosol-forming material, for example.

12. An aerosol-generating article according to any one of claims 1 to 10, wherein the hollow tubular section is a tube of extruded aerosol-forming material, such as a tube of extruded homogenized tobacco material or such as a tube of extruded smokeless aerosol-forming material.

13. A method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, for example according to any of claims 1 to 12, the method comprising:

casting and drying the slurry to form a sheet of aerosol-forming material, and

the sheet is formed into a hollow tube.

14. The method of claim 13, wherein forming the slurry comprises:

forming a first mixture comprising:

an aerosol former;

a fiber;

water;

optionally, an acid; and

optionally, a composition comprising nicotine,

forming a second mixture comprising:

the thermally conductive particles; and

the presence of the binder is not limited to a specific type,

and adding the second mixture to the first mixture to form a combined mixture.

15. An aerosol-generating system comprising an aerosol-generating article according to any of claims 1 to 12 and an electrically powered aerosol-generating device, preferably wherein the electrically powered aerosol-generating device is configured to resistively heat the aerosol-generating article in use, or wherein the electrically powered aerosol-generating device is configured to inductively heat the aerosol-generating article, such as the aerosol-forming substrate of the aerosol-generating article, in use.