ES3033434T3 - Article with tubular aerosol-forming substrate - Google Patents

Abstract

An aerosol-generating article for producing an inhalable aerosol by heating comprises several components, including an aerosol-forming substrate. This substrate is in the form of a hollow tubular segment defining a cavity extending between an upstream end and a downstream end of the aerosol-forming substrate. The aerosol-forming substrate comprises several thermally conductive particles and an aerosol former. The combination of tubular geometry and thermally conductive particles allows for a faster first puff, more efficient aerosol extraction, and a lighter weight of the aerosol-generating article. (Automatic translation with Google Translate, no legal value)

Description

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 for 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 burned, are known in the art. Typically, in such heated smoking articles, an aerosol is generated by heat transfer from a heat source to a physically separate aerosol-generating material or substrate, which may be located in contact with, within, 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 are entrained in the air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

A number of prior art documents describe 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 the transfer of heat from one or more electrical heating elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article. For example, electrically heated aerosol-generating devices have been proposed comprising an internal heating sheet adapted to be inserted into the aerosol-generating substrate. It is also known to use an aerosol-generating article in combination with an external heating system. For example, WO-A-2020/115151 describes the provision of an external heating element disposed around the periphery of the aerosol-generating article when the aerosol-generating article is received in a cavity of the aerosol-generating device. Alternatively, inductively heatable aerosol-generating articles comprising an aerosol-generating substrate and a susceptor disposed within the aerosol-generating substrate have been proposed by WO-A-2015/176898.

In general, it can be difficult to provide efficient heating of an aerosol-generating substrate along the entire length of the substrate rod. The portions of the substrate closest to the heating element will inevitably be heated most effectively, while imperfect heat transfer through the substrate will mean that portions of the substrate further from the heating element may not be heated effectively. Aerosol generation from these portions of the substrate that are not effectively heated is therefore not optimal, and in some cases, portions of the substrate may not reach a sufficiently high temperature during use for an aerosol to be generated at all. For example, when an external heating element is used to heat an aerosol-generating substrate rod, as described above, the central portion of the aerosol-generating substrate rod is unlikely to generate as much aerosol as the outer portions of the rod, and in some cases, it may not generate any aerosol at all. Overall, aerosol generation from the aerosol-generating rod is therefore likely to be inefficient, with possible waste of a portion of the aerosol-generating substrate.

Furthermore, the aerosol-generating substrate generally does not immediately generate aerosol upon activation of a heating element. This is because there is a preheating time after activation of a heating element, during which the aerosol-generating substrate is heated to a temperature required for aerosol generation. As such, there may be a relatively long duration between activation of a heating element and the generation of a sensorially acceptable aerosol for inhalation by a user.

WO 2020/025701 relates to an aerosol-generating substrate comprising an aerosol-generating material, wherein the aerosol-generating material comprises an amorphous solid, the amorphous solid comprising: 1-60% by weight of a gelling agent; 5-80% by weight of an aerosol-generating agent; and 1-70% by weight of an active ingredient; wherein these weights are calculated on a dry weight basis; wherein bimodal or multimodal release of one or more active ingredients from the amorphous solid is observed during use. It would therefore be desirable to provide an aerosol-generating article having an aerosol-generating substrate that is adapted to provide more efficient aerosolization of the aerosol-generating substrate and to reduce waste of substrate materials, such as tobacco. It would also be desirable to provide such an aerosol-generating article that can achieve a relatively short preheating time so that a sensorially acceptable aerosol can be delivered to a user shortly after the start of heating of the aerosol-generating substrate. It would also be desirable to provide such an aerosol-generating article that can provide an optimized delivery of aerosol from the aerosol-generating substrate. It would be particularly desirable to provide such an aerosol-generating article with a relatively simple design so that it can be manufactured cost-effectively and incorporated into existing product designs. It would be desirable to provide such an article that can be easily adapted so that it can be heated in a variety of types of heating devices, including inductive and resistive heating devices.

Known aerosol-forming substrates have relatively low thermal conductivities. The low thermal conductivity of an aerosol-forming substrate can lead to a relatively large temperature gradient across the aerosol-forming substrate during use. This can mean that portions of the aerosol-forming substrate that are located farther from a heating element do not reach a high temperature and therefore do not release as many volatile compounds as they would if the aerosol-forming substrate had a higher thermal conductivity. In other words, the low thermal conductivity of the aerosol-forming substrate can undesirably result in low efficiency of use of the aerosol-forming substrate. The invention is defined by the appended claims.

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

For example, an aerosol-generating article may be provided for producing an inhalable aerosol upon heating, the aerosol-generating article comprising a plurality of components including 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 former.

The use of a tubular geometry for the aerosol-forming substrate can help avoid the effects of thermal gradients on substrate heating. With a tubular geometry, the substrate has no core, and the aerosol-forming material is concentrated in regions of the substrate that are heated, either internally or externally. This allows extraction efficiency to be significantly increased, which in turn can reduce the total amount of substrate required for a user experience. A reduction in substrate mass reduces heating inertia and therefore can reduce the time required to heat to a sufficient temperature, thereby reducing the time to first puff. The use of a thermally conductive substrate can significantly enhance the advantages gained by adopting a tubular substrate geometry. A substrate with increased thermal conductivity, or increased as a result of the presence of thermally conductive particles, can further reduce substrate inertia and can further reduce the time to first puff and increase overall extraction efficiency. By selecting specific thermally conductive particles, for example, graphite or expanded graphite, the substrate weight can be further reduced. Reducing the total mass of the aerosol-forming substrate required for a suitable user experience has several advantages, including a reduction in overall thermal inertia and a reduction in the weight of an aerosol-generating article comprising the substrate. Reducing the weight of an article can provide reduced shipping costs and reduced energy involved in shipping, and may also provide tax benefits in certain jurisdictions.

An aerosol-generating article according to the present invention may be particularly advantageously employed in an aerosol-generating system employing progressive heating, or zonal heating. An aerosol-generating article according to the present invention may also be particularly advantageously employed in an aerosol-generating system employing puff-on-demand heating.

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

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

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

When the term “thermally conductive particles” is used to refer to particles comprising carbon, for example particles comprising or consisting of one or more of graphite, expanded graphite, graphene, carbon nanotubes, carbon and diamond, the thermally conductive particles may be referred to as carbon particles or carbon-containing particles.

Advantageously, the thermally conductive particles can increase the thermal conductivity of the aerosol-forming substrate. Increasing the thermal conductivity of the substrate can provide a more uniform temperature distribution across the substrate during use. This can result in a greater proportion of the aerosol-forming substrate reaching a temperature high enough to release volatile compounds, and therefore greater efficiency of use of the aerosol-forming substrate. Furthermore, the increased thermal conductivity of the substrate can allow a heater, e.g., a heating sheet configured to heat the substrate, to operate at a lower temperature and therefore require less energy. Furthermore, the increased thermal conductivity of the substrate can allow a heater to heat the substrate to a temperature at which volatile compounds are released in less time. Therefore, the increased thermal conductivity can reduce the time required to form an inhalable aerosol for a user.

Advantageously, one or both of the fibers and the binder can increase the tensile strength of the material forming the aerosol-forming substrate. The increased tensile strength can, for example, allow the production of a sheet of the aerosol-forming material using existing production machinery, which can then be formed into a tube to form the 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 0.5 W/(mK) in at least one direction, or in all directions, at 25 degrees Celsius. This thermal conductivity may be measured when the moisture content of the substrate is between 0 and 20, or 5 and 15, for example about 10%. This thermal conductivity may be measured when the substrate comprises between 0 and 20, or 5 and 15, for example about 10% by weight of water. The moisture or water content of the substrate may be measured by using a titration method. The moisture or water content of the substrate may be measured by 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% by weight of 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 carbon particles. Optionally, some or all of the thermally conductive particles are diamond particles, for example, artificial diamond particles. Advantageously, such materials can have relatively high thermal conductivities.

Expanded graphite may have a density less than 2, 1.8, 1.5, 1.2, 1, 0.8, or 0.5, 0.2, 0.1, 0.05, 0.02 grams per cubic centimeter (g/cm3). Expanded graphite may have a density 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 per cubic centimeter (g/cm3). Expanded graphite may have a density between 0.01 and 3, 0.01 and 2, 0.01 and 1.8, 0.01 and 1.5, 0.01 and 1.2, 0.01 and 1, 0.01 and 0.8, 0.01 and 0.5, 0.02 and 3, 0.02 and 2, 0.02 and 1.8, 0.02 and 1.5, 0.02 and 1.2, 0.02 and 1, 0.02 and 0.8, 0.02 and 0.5, 0.01 and 3, 0.05 and 2, 0.05 and 1.8, 0.05 and 1.5, 0.05 and 1.2, 0.05 and 1, 0.05 and 0.8, 0.05 and 0.5 g/cm3, 0.1 and 3, 0.1 and 2, 0.1 and 1.8, 0.1 and 1.5, 0.1 and 1.2, 0.1 and 1, 0.1 and 0.8, 0.1 and 0.5, 0.2 and 3, 0.2 and 2, 0.2 and 1.8, 0.2 and 1.5, 0.2 and 1.2, 0.2 and 1, 0.2 and 0.8, 0.2 and 0.5, 0.5 and 3, 0.5 and 2, 0.5 and 1.8, 0.5 and 1.5, 0.5 and 1.2, 0.5 and 1, 0.5 and 0.8, 0.8 and 3, 0.8 and 2, 0.8 and 1.8, 0.8 and 1.5, 0.8 and 1.2, 0.8 and 1 grams per cubic centimeter (g/cm3).

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

Optionally, in accordance with alternative embodiments, where each of the thermally conductive particles does not necessarily consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, carbon, 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 can have relatively high thermal conductivities.

Thermally conductive particles can each have a "particle size." The meaning of the term "particle size" and a method for measuring particle size are explained below.

Thermally conductive particles can be characterized by a particle size distribution. The particle size distribution can have D10, D50, and D90 particle sizes. The D10 particle size is defined such that 10% of the particles have a particle size less than or equal to the D10 particle size. Similarly, the D50 particle size is defined such that 50% of the particles have a particle size less than or equal to the D50 particle size. Therefore, the D50 particle size can be referred to as the median particle size. The D90 particle size is defined such that 90% of the particles have a particle size less than or equal to the D90 particle size. Therefore, if there were 1000 particles in the distribution and the particles were sorted by ascending particle size, the D10 particle size number would be expected to be approximately equal to the particle size of the 100th particle, the D50 particle size should be approximately equal to the particle size of the 500th particle, and the D90 particle size number to be approximately equal to the particle size of the 900th particle.

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

Optionally, the thermally conductive particles have a particle size distribution having a numerical D10 particle size, wherein the numerical 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 numerical D10 particle size, wherein the numerical D10 particle size is no more than 1000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

A compromise must be reached when deciding on particle sizes. Larger thermally conductive particles can advantageously increase the thermal conductivity of the aerosol-forming substrate more than smaller thermally conductive particles. However, larger thermally conductive particles can reduce the space available for the aerosol-forming material on the substrate.

Optionally, the thermally conductive particles have a particle size distribution having a numerical D50 particle size, wherein the numerical 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 numerical D50 particle size, wherein the numerical D50 particle size is no more than 1000, 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 numerical D90 particle size, wherein the numerical 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 numerical D90 particle size, wherein the numerical D90 particle size is no more than 1000, 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 numerical D10 particle size and a numerical D90 particle size, wherein the numerical D90 particle size is no more than 50, 40, 30, 20, 10, or 5 times the numerical D10 particle size.

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

A compromise may be necessary regarding the particle size distribution. A tighter particle size distribution, for example characterized by a smaller ratio between the D90 and D10 particle sizes, may advantageously provide more uniform thermal conductivity across the aerosol-forming substrate. This is because there will be less variation in particle size at different locations on the substrate. This may advantageously allow more efficient use of the aerosol-forming material along the aerosol-forming substrate. However, a tighter particle size distribution may disadvantageously be more difficult and expensive to achieve. The inventors have discovered that the particle size distributions described above can provide an optimal compromise between these two factors.

Optionally, the thermally conductive particles have a particle size distribution having a D10 particle size by volume, wherein the D10 particle size by volume 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 D10 particle size by volume, wherein the D10 particle size by volume is no more than 1000, 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 D50 particle size by volume, wherein the D50 particle size by volume 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 D50 particle size by volume, wherein the D50 particle size by volume is no more than 1000, 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 D90 particle size by volume, wherein the D90 particle size by volume 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 D90 particle size by volume, wherein the D90 particle size by volume is no more than 1000, 500, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns.

It may be particularly preferable for the thermally conductive particles to have a particle size distribution having a D10 particle size by volume between 1 and 20 microns. Alternatively, or in addition, it may be particularly preferable for the thermally conductive particles to have a particle size distribution having a D90 particle size by volume between 50 and 300 microns, or between 50 and 200 microns.

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

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

As explained above, a compromise must be made regarding the particle size distribution, and the inventors have discovered that the above particle size distributions can provide an optimal 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 more than 1000, 500, 300, 200, 100, 50, 20, 10, 5, 2, 1, 0.5, or 0.2 microns. It may be particularly preferable for each of the thermally conductive particles to have a particle size of at least 1 micron. Alternatively, or in addition, it may be particularly preferable for each of the thermally conductive particles to have a particle size of no more than 300 microns. Particles smaller than 1 micron can be difficult to handle during manufacturing. Furthermore, particles smaller than 1 micron may be more likely to pass through a filter in an aerosol-generating article comprising the aerosol-forming substrate. Particles larger than 300 microns can occupy a significant amount of space in the substrate that could be used for aerosol-forming material. Therefore, it may be particularly advantageous for each of the thermally conductive particles to 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 larger of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a smaller of the three dimensions. Optionally, each of the thermally conductive particles has three mutually perpendicular dimensions, a larger of the three dimensions being no more than 10, 8, 5, 3, or 2 times larger than a second larger of the three dimensions. Optionally, each of the thermally conductive particles is essentially spherical. Advantageously, the orientation of essentially spherical particles may not affect the thermal conductivity of the substrate as much as the orientation of non-spherical particles. Therefore, the use of more spherical particles may result in less variability between different substrates where the particle orientations are not controlled. Furthermore, essentially 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 the thermal conductivity of the substrate to be more uniform.

Optionally, the substrate comprises, on a dry weight basis, at least 20, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or 85% by weight of the thermally conductive particles. Optionally, the substrate comprises, on a dry weight basis, no more than 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20 or 15% by weight of the thermally conductive particles. Optionally, the substrate comprises, on a dry weight basis, between 10 and 90, 20 and 90, 30 and 90, 40 and 90, 50 and 90, 60 and 90, 70 and 90, 80 and 90, 10 and 80, 20 and 80, 30 and 80, 40 and 80, 50 and 80, 60 and 80, 70 and 80, 10 and 70, 20 and 70, 30 and 70, 40 and 70, 50 and 70, 60 and 70, 10 and 60, 20 and 60, 30 and 60, 40 and 60, 50 and 60, 10 and 50, 20 and 5 ...50 and 60, 10 and 50, 20 and 50, 30 and 60, 60 and 70, 70 and 80, 80 and 90, 90 and 100, 110 and 120, 130 and 140, 150 and 160, 170 and 180, and 50, 40 and 50, 10 and 40, 20 and 40, 30 and 40, 10 and 30, 20 and 30, or 10 and 20% by weight of the thermally conductive particles. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 50 and 90, or more preferably between 60 and 90, or even more preferably between 65 and 85,% by weight of the thermally conductive particles.

A compound may be required relative to the weight percent of thermally conductive particles in the substrate. 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 may also reduce the space available for one or more of the aerosol-former, binder, and fibers, potentially resulting in a substrate that forms less aerosol or has lower tensile strength.

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

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

Optionally, the substrate comprises, on a dry weight basis, at least 2, 4, 6, 8, 10, 12, 14, 16, or 18% by weight of the fibers. Optionally, the substrate comprises, on a dry weight basis, no more than 20, 18, 16, 14, 12, 10, 8, 6, or 4% by weight of the fibers. Optionally, the substrate comprises, on a dry weight basis, between 4 and 20, 6 and 20, 8 and 20, 10 and 20, 12 and 20, 14 and 20, 16 and 20, 18 and 20, 2 and 18, 4 and 18, 6 and 18, 8 and 18, 10 and 18, 12 and 18, 14 and 18, 16 and 18, 2 and 16, 4 and 16, 6 and 16, 8 and 16, 10 and 16, 12 and 16, 14 and 16, 2 and 14, 4 and 14, 6 and 14, 8 and 14, 10 and 14, 12 and 14, 2 and 12, 4 and 12, 6 and 12, 8 and 12, 10 and 12, 2 and 10, 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, or 2 and 4% by weight of the fibers. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 2 and 10% by weight of the fibers.

Optionally, the fibers are cellulosic fibers. Advantageously, cellulose fibers are not excessively expensive and can increase the substrate's tensile strength.

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

Optionally, the substrate comprises, on a dry weight basis, at least 4, 6, or 8% by weight of the binder. Optionally, the substrate comprises, on a dry weight basis, no more than 8, 6, or 4% by weight of the binder. Optionally, the substrate comprises, on a dry weight basis, between 4 and 10, 6 and 10, 8 and 10, 2 and 8, 4 and 8, 6 and 8, 2 and 6, 4 and 6, 2 and 4% by weight of the binder. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 2 and 10% by weight of the binder.

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 gum; alginate; starches, such as modified or derivatized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl, and carboxymethylcellulose; tamarind gum; dextran; pullalon; konjac flour; xanthan gum, and the like. It may be particularly preferable for the binder to be or comprise guar. It may be particularly preferable for the binder to comprise or consist of one or more of carboxymethylcellulose or hydroxypropylcellulose or a gum such as guar gum. Optionally, the thermally conductive particles are distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the aerosol-forming agent is distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the fibers are distributed substantially homogeneously throughout the aerosol-forming substrate. Optionally, the binder is distributed substantially homogeneously throughout the aerosol-forming substrate. Advantageously, a homogeneous distribution of the substrate components can result in the substrate having more spatially uniform properties. For example, substantially homogeneously distributed thermally conductive particles can result in the substrate having substantially uniform thermal conductivity. As another example, a substantially homogeneously distributed binder or fibers can result in the substrate having substantially uniform tensile strength.

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

Optionally, the nicotine is distributed essentially homogeneously throughout the aerosol-forming substrate.

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

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

Optionally, the acid is distributed essentially homogeneously throughout the aerosol-forming substrate.

Optionally, the substrate comprises at least one botanical. Optionally, the substrate comprises, on a dry weight basis, at least 0.01, 1, 2, 5, 10, or 15% by weight of at least one botanical plant. Optionally, the substrate comprises, on a dry weight basis, no more than 20, 15, 10, 5, 2, or 1% by weight of at least one botanical plant. Optionally, the substrate comprises, on a dry weight basis, 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 at least one botanical. It may be particularly preferable that the substrate comprises, on a dry weight basis, between 1 and 15% by weight of the at least one botanical.

Optionally, the at least one botanical comprises or consists of one or both of clove and rosemary.

Optionally, the at least one botanical is distributed essentially homogeneously throughout the aerosol-forming substrate.

Optionally, the substrate comprises at least one flavoring. Optionally, the substrate comprises, on a dry weight basis, at least 0.1, 1, 2, or 5% by weight of the at least one flavoring. Optionally, the substrate comprises, on a dry weight basis, no more than 10, 5, 2, or 1% by weight of the at least one flavoring. Optionally, the substrate comprises, on a dry weight basis, 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% by weight of the at least one flavoring. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.1 and 5% by weight of the at least one flavoring.

Optionally, the at least one flavoring agent is present as a coating, for example, a coating on one or more components of the aerosol-forming substrate. Alternatively, or in addition, the at least one flavoring agent is distributed substantially homogeneously 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 grass leaf, tobacco leaf, tobacco rib fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, and expanded tobacco. Optionally, the at least one organic material is substantially homogeneously distributed throughout the aerosol-forming substrate.

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

The substrate is in the form of a tube having an external diameter and an internal diameter, the internal diameter being between 2.5 mm and 19 mm

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 5 mm and 100 mm, the outer diameter is between 3 mm and 20 mm, and the inner diameter is between 2.5 mm and 19 mm. The length of the tube may be between 8 mm and 25 mm, the outer diameter of the tube may be between 6 mm and 8 mm, and the inner diameter of the tube may be between 5 mm and 7.9 mm.

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

Alternatively, there may be no susceptor materials present in the aerosol-forming substrate or in the aerosol-forming substrate rod.

Optionally, some or each of the thermally conductive particles may be inductively heatable, for example to a temperature of at least 100, 150, or 200 degrees Celsius. Optionally, some or each of the thermally conductive particles comprise or consist of one or more susceptor materials. Advantageously, this may allow the thermally conductive particles to be inductively heated. The thermally conductive particles may comprise or be the only susceptor material(s) present in the aerosol-forming substrate or in the aerosol-forming substrate rod. That is, there may be no susceptor elements present in the aerosol-forming substrate or in the aerosol-forming substrate rod except for the thermally conductive or carbon particles.

Suitable susceptor materials include, but are not limited to: carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminum, nickel, nickel-containing compounds, titanium, and compounds of metallic materials. Suitable susceptor materials may comprise a ferromagnetic material, for example, ferritic iron, a ferromagnetic alloy, such as ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. A suitable susceptor material may be or comprise aluminum. A susceptor material preferably comprises more than 5 percent, preferably more than 20 percent, more preferably more than 50 percent, or more than 90 percent ferromagnetic or paramagnetic materials. Preferred susceptor materials may comprise a metal, metal alloy, or carbon.

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

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 500 W/(mK) in at least one direction at 25 degrees Celsius.

Optionally, the aerosol-forming substrate has a density of no more than 1500, 1450, 1400, 1350, 1300, 1250, 1200, 1100, 1050, 1000, 950, 900, 850, 800, 850, 800, 750, 700, 650, or 600 kg/m3. Optionally, the aerosol-forming substrate has a density between 600 and 1400, 800 and 1200, or 900 and 1100 kg/m3. Advantageously, reducing the density of the substrate may reduce transportation costs of the substrate.

Optionally, the aerosol-forming substrate has a moisture content of between 1 and 20, or 3 and 15% by weight. This moisture content can be measured after 48 hours of equilibration at 50% relative humidity at 20 degrees Celsius. Optionally, the aerosol-forming substrate comprises between 1 and 20, or 3 and 15% by weight of water. The moisture or water content of the substrate can be measured using a titration method. The moisture or water content of the substrate can be measured using the Karl Fischer method.

Optionally, the aerosol-forming substrate is formed from a sheet of aerosol-forming material that is rolled to form the tubular segment. Thus, the hollow tubular segment may be a rolled sheet of aerosol-forming material, for example, a rolled sheet of homogenized tobacco material, or, for example, a rolled sheet of tobacco-free aerosol-forming material.

The aerosol-forming substrate may have a thickness equivalent to a single layer of the aerosol-forming material sheet. The aerosol-forming substrate may have a thickness equivalent to two or more layers of the sheet. The aerosol-forming material sheet 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 more than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the sheet may have a thickness between 100 and 350, or 150 and 300 microns.

Optionally, the sheet of aerosol-forming material has a grammage of at least 20, 50, or 100 g/m2. Optionally, the sheet or strip has a grammage of no more than 300 g/m2. Optionally, the sheet has a grammage of between 20 and 300, between 50 and 250, or between 100 and 250 g/m2.

Optionally, the sheet has a density of at least 0.1, 0.2, 0.3, or 0.5 g/m3. Optionally, the sheet has a density of no more than 2, 1.5, 1.2, or 1 g/m3. Optionally, the sheet has a density between 0.1 and 2, 0.2 and 2, 0.3 and 2, 0.3 and 1.5, or 0.3 and 1.2 g/m3.

The hollow tubular segment may be an extruded tube of aerosol-forming material, for example, an extruded tube of homogenized tobacco material or, for example, an extruded tube of tobacco-free aerosol-forming material.

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

Optionally, the aerosol-generating article comprises a front cap. 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 vents. Optionally, the aerosol-generating article comprises a mouth cap filter. Optionally, the aerosol-generating article comprises a wrapper, for example, a paper wrapper.

Optionally, the front plug is disposed at the most upstream end of the article. Optionally, the aerosol-forming substrate is disposed downstream of the front plug. Optionally, the first hollow tube is disposed downstream of the aerosol-forming substrate. Optionally, the second hollow tube is disposed downstream of the first hollow tube. Optionally, the mouth plug filter is disposed downstream of one or both of the first hollow tube and the second hollow tube. Optionally, the mouth plug filter is disposed at the most downstream end of the article. Optionally, the most downstream end of the article, which may be referred to as the mouth end of the article, may be configured for insertion into a user's mouth. A user may be able to inhale, for example, directly into the mouth-side end of the article.

Optionally, the front cap, the tubular aerosol-forming substrate, one or both of the first hollow tube and the second hollow tube, and the mouth cap filter are circumscribed by a wrapper, for example, a paper wrapper.

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

One or more of the front cap, the aerosol-forming substrate, the first hollow tube, the second hollow tube, and the mouth cap filter may be substantially cylindrical in shape, for example, right cylindrical.

In accordance with one aspect of the present disclosure, an aerosol generating system is provided.

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

Optionally, the electric aerosol generating device is configured to resistively heat the aerosol generating article in use.

Optionally, the electric aerosol-generating device is configured to inductively heat the aerosol-generating article, e.g., the aerosol-forming substrate of the aerosol-generating article, during use. In accordance with the present disclosure, a method is provided for forming a hollow tubular aerosol-forming substrate, e.g., a substrate for an aerosol-generating article as described above. The method may comprise forming a slurry comprising one or more or all of the thermally conductive particles, the aerosol former, the fibers, and the binder. The method may comprise melting and drying the slurry to form the aerosol-forming substrate, or extruding the slurry to form the aerosol-forming substrate, or melting and drying the slurry to form a precursor such as a sheet of aerosol-forming material and then forming the precursor into the aerosol-forming substrate.

Optionally, the suspension contains water. Optionally, the suspension comprises between 20 and 90, 30 and 90, 40 and 90, 40 and 85, 50 and 80, 60 and 80, or 60 and 75% by weight of water.

Optionally, the suspension 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 suspension comprises nicotine.

Optionally, forming the suspension comprises forming a first mixture. The first mixture may comprise the aerosol former. The first mixture may comprise the fibers. The first mixture may comprise water. The first mixture may comprise the acid. The first mixture may comprise nicotine. Forming the suspension may comprise forming a second mixture. The second mixture may comprise the thermally conductive particles. The second mixture may comprise the binder. Forming the suspension may comprise adding the second mixture to the first mixture to form a blended mixture.

Therefore, the formation of the suspension may comprise:

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

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

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

The combined mixture may be subsequently formed in the suspension, for example by mixing. Optionally, forming the first mixture comprises providing the aerosol former or a solution comprising the aerosol former and nicotine.

Optionally, forming the first mixture comprises adding the acid to the aerosol former or the solution comprising the aerosol former and nicotine to form a first premix.

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

Optionally, forming the second mixture comprises mixing the thermally conductive particles and the binder.

Optionally, the method, for example the slurry-forming step, comprises a first mixing of the combined mixture. Optionally, the first mixing occurs under a first pressure of no more than 500, 400, 300, 250, or 200 mbar. Optionally, the first mixing occurs for between 1 and 10, 2 and 8, or 3 and 6 minutes, for example for about 4 minutes.

Optionally, the method, for example the suspension-forming step, comprises, after the first mixing, a second mixing. Optionally, the second mixing occurs under a second pressure that is lower than the first pressure. Optionally, the second pressure is no more than 500, 400, 300, 200, 150, or 100 mbar. Optionally, the second mixing occurs for between 5 and 120, 5 and 80, 5 and 40, or 10 and 30 seconds, for example around 20 seconds.

Optionally, casting the suspension comprises casting the suspension on a flat support, for example, a flat steel support.

Optionally, after melting the slurry and before drying the slurry, the method comprises establishing a thickness of the slurry, for example establishing a thickness of the slurry between 100 and 1200, 200 and 1000, 300 and 900, 500 and 700 microns, for example about 600 microns.

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

Optionally, drying the suspension forms the precursor to form the aerosol-forming substrate, the precursor being a sheet of aerosol-forming material. Optionally, the method comprises cutting the sheet of aerosol-forming material.

A sheet of aerosol-forming material can be formed on the aerosol-forming substrate by rolling the sheet of aerosol-forming substrate into a tube. The walls of the tube are therefore formed from the sheet of aerosol-forming material. The tubular shape can be maintained by overlapping a portion of the rolled sheet and securing the overlapped portion with an adhesive such as glue. The walls of the tube formed by rolling the sheet of aerosol-forming material can have a thickness equal to the thickness of the sheet of aerosol-forming material; that is, the tube can be formed from a single layer of the sheet of aerosol-forming material. However, the walls of the tube can be formed from multiple layers of the sheet rolled into the shape of a tube. Once rolled and secured, the tube of aerosol-forming material can be cut into lengths to form tubular segments of aerosol-forming substrate.

As will be understood by the skilled person who has read this description, the features described in this description in relation 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 capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate may comprise an aerosol-forming material. An aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or support. An aerosol-forming substrate may conveniently be part of an aerosol-generating article or a smoking article.

As used herein, the term “thermally conductive particles” may refer to particles having a thermal conductivity greater than 0.3, preferably 0.5, or more preferably 1 W/(mK) in at least one direction at 25 degrees Celsius, for example in all directions at 25 degrees Celsius. 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. Expanded graphite may have layers of carbon (similar to graphite, for example) with a separation between the carbon layers greater than the separation found between carbon layers in regular graphite. 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 dimension and may be used to characterize the size of a given particle. The dimension may be the diameter of a spherical particle that occupies the same volume as the given particle. All particle sizes and particle size distributions in the present disclosure may be obtained by using a standard laser diffraction technique. The particle sizes and particle size distributions as indicated in the present disclosure may be obtained by using a commercially available sensor, for example, a Sympatec HELOS laser diffraction sensor.

As used herein, unless otherwise specified, the term “density” may be used to refer to the true density. Thus, unless otherwise specified, the density of a powder or plurality of particles may refer to the true density of the powder or plurality of particles (as opposed to the bulk density of the powder or plurality of particles, which can vary greatly depending on how the powder or plurality of particles is handled). Measurement of true density can be performed using several standard methods, often based on Archimedes' principle. The most commonly used method, when used to measure the true density of a powder, involves placing the powder into a container (a pycnometer) of known volume and weighing it. The pycnometer is then filled with a fluid of known density, in which the powder is not soluble. The volume of the powder is determined by the difference between the volume indicated by the pycnometer and the volume of liquid added (i.e., the volume of air displaced).

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 flat sheet-like element having a width and length that are substantially greater than, for example, at least 2, 3, 5, 10, 20, or 50 times its thickness.

As used herein, the term "aerosol-forming agent" may refer to any suitable known compound or mixture of compounds that, in use, facilitates the formation of an aerosol. The aerosol may be a dense, 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, the term “aerosol cooling element” may refer to a component of an aerosol-generating article located downstream of the aerosol-forming substrate such that, during use, an aerosol formed by the substrate or by volatile compounds released from the aerosol-forming substrate passes therethrough and is cooled by the aerosol cooling element before being inhaled by a user.

As used herein, the term “bar” may refer to a generally cylindrical element, for example, straight cylindrical, of essentially circular, oval or elliptical cross-section.

As used herein, the term "vent level" may refer to a volume ratio between the airflow admitted to an aerosol-generating article through the ventilation zone (vent airflow) and the sum of the aerosol airflow and the ventilation airflow. The higher the ventilation level, the greater the dilution of the aerosol flow delivered to the consumer.

The examples will now be described in more detail with reference to the figures in which:

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

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

Figure 3 shows a schematic cross-sectional view of a second embodiment of an aerosol generating system, comprising the article of Figure 1; and

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

Figure 1 shows a schematic cross-sectional view of an illustrative aerosol-generating article 10 in accordance with one embodiment of the invention. The aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or proximal end or buccal 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 a wrapper 70. The plurality of elements forming the article are, from the distal end to the proximal end, a front cap 46, a tubular segment of thermally enhanced aerosol forming substrate 12, a cardboard tube free flow filter 34 and a mouthpiece filter 42. The wrapper 70 is a cigarette paper.

The front plug 46, also referred to as the upstream element, is located immediately upstream of the tubular aerosol-forming substrate 12. The front plug 46 is provided in the form of a cylindrical plug of cellulose acetate. The front plug 46 has a diameter of approximately 7.2 mm and a length of approximately 5 millimeters. The RTD of the front plug 46 is approximately 30 millimeters H2O.

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

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

The nozzle element 42 is provided in the form of a cylindrical plug of low-density cellulose acetate. The nozzle element 42 has a length of approximately 12 millimeters and an external diameter of approximately 7.2 mm. The RTD of the nozzle element 42 is approximately 12 millimeters of H2O. It should be understood that the configuration of the aerosol-generating article 10 of Figure 1 is intended to serve only as an example. The thermally enhanced, tubular aerosol-forming substrate 12 could, for example, be employed in an aerosol-generating article that is longer, for example 80 mm long, and thinner, for example 4.5 mm in diameter.

In a specific embodiment of an aerosol-generating article as illustrated in Figure 1, the tubular segment 12 of the aerosol-forming substrate comprises, on a dry weight basis, about 76.1% by weight of thermally conductive particles 44. In this embodiment, the thermally conductive particles 44 are graphite particles, specifically FP 99.5 graphite particles (>99.5% purity) from Graphit Kropfmül GmbH, AMG Graphite Gk, although other particles or mixtures of particles could be used. Each thermally conductive particle has a thermal conductivity of about 6 W/(mK) in at least one direction at 25 degrees Celsius. The tubular aerosol-forming substrate 12 comprises, on a dry weight basis, about 17.7% by weight of an aerosol former. In this embodiment, the aerosol former is glycerol, specifically ICOF Europe food grade glycerol (>99.5% purity).

The tubular aerosol-forming substrate 12 comprises, on a dry weight basis, about 3.9% by weight of fibers. In this embodiment, the fibers are cellulose fibers, specifically birch cellulose fibers from Stora Enso OYJ.

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

The tubular aerosol-forming substrate comprises approximately 10% by weight of 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 such as fumaric acid, a plant such as clove or rosemary, and a flavoring.

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

Each of the thermally conductive particles 44 has an essentially spherical shape. The thermally conductive particles 44 are distributed essentially homogeneously throughout the aerosol-forming substrate. The particle size distribution has a D10 particle size by volume of about 6 microns, a D50 particle size by volume of about 20 microns, and a D90 particle size by volume of about 56 microns. Each of the thermally conductive particles 44 has a particle size greater than about 1 micron and less than about 300 microns.

Thermally conductive particles 44 have a density of about 2,200 kilograms per cubic meter. The aerosol-forming substrate has a density of about 800 kilograms per cubic meter.

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

A suspension is formed using a laboratory disperser capable of mixing viscous liquids, dispersing powders throughout liquids, and removing gases from a mixture (e.g., by applying a vacuum or other suitably low pressure). In this embodiment, a commercially available laboratory disperser from PC Laborsystem was used.

To form the suspension, a first mixture is formed by adding approximately 7.11 grams of the aerosol former to the blade disperser, followed by approximately 157.5 grams of water, and approximately 1.57 grams of fibers. These first ingredients are then mixed at 25 degrees Celsius for 5 minutes at 600-700 rpm to ensure a homogeneous mixture and to hydrate the fibers. A second mixture is then formed by manually mixing approximately 32.95 grams of the thermally conductive particles and approximately 0.92 grams of the binder. This mixing of the second mixture prevents clumping in the laboratory dispersion. The second mixture is then added to the first mixture to form a blended mixture. The blended mixture is then mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of approximately 200 mbar. The reduced pressure can help ensure that the thermally conductive particles are evenly dispersed throughout the mix and that there is little entrapped air and few lumps in the blended mix. The blended mix is then mixed at 5,000 rpm for 20 seconds at 25 degrees Celsius and a second reduced pressure of around 100 mbar. This second reduced pressure can help eliminate any remaining air bubbles. This forms a slurry for molding.

The suspension is then melted and dried using a suitable apparatus. This method uses a commercially available Mathis Labcoater. This apparatus includes a flat stainless steel support and a comma blade to adjust the thickness of the molten suspension on the support.

The suspension is poured onto the flat support, and the gap between the comma blade and the flat support is set at 0.6 millimeters. This ensures that the suspension thickness does not exceed 0.6 millimeters at any given point.

The suspension is then dried with hot air at a temperature of between 120 and 140 degrees Celsius for 2 to 5 minutes. After this drying, a film of the aerosol-forming substrate is formed. This film has a thickness of approximately 300 microns, a weight of approximately 250 grams per square meter, and a density of approximately 0.79 kilograms per cubic meter.

The sheet is then rolled up to form a tube. Adhesive is applied to an overlapping portion of the rolled sheet to secure the sheet into a tube shape, and the tube is then cut into 12 mm lengths to form 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 wrapping the components in the wrapper 70.

Other embodiments may have the same structure as described above, but have an aerosol-forming substrate of a different composition. For example, in a further embodiment, the aerosol-forming material comprises a thermally enhanced homogenized tobacco tube comprising thermally conductive particles 44. The thermally conductive particles 44 are carbon particles, specifically expanded graphite particles, having a particle size distribution with a D10 particle size of 6.6 microns, a D50 particle size of 20 microns, and a D90 particle size of 56 microns. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume average particle size of about 35 microns. Each of the expanded graphite particles is essentially spherical in shape. The expanded graphite particles have a density of less than 1000 kilograms per cubic meter. The aerosol-forming substrate, which includes the aerosol-forming material and the thermally conductive particles 44, has a combined density of approximately 760 kilograms per cubic meter. The expanded graphite particles constitute approximately 5% of the aerosol-forming substrate by weight.

The aerosol-forming substrate tube 12 is formed by a process that includes the following steps:

• premixing a binder, guar gum, with an aerosol former, glycerin, to form a first premix;

• premixing finely chopped tobacco material and a powder consisting of the expanded graphite particles 44 and having a bulk density of about 0.065 grams per cubic centimeter, to form a second premix;

• mix the first and second premixes with water to form a suspension;

• homogenize the suspension by using a high shear mixer;

• pour the suspension onto a conveyor belt;

• controlling the thickness of the suspension and drying it to form an aerosol-forming substrate sheet; and

• roll the aerosol-forming substrate sheet into a tube and cut the tube to form tubular segments of aerosol-forming substrate.

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

Figure 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 Figure 1.

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

The aerosol generating device 102 further comprises a housing 110 defining an essentially cylindrical cavity for receiving a portion of the article 10. The heating sheet 108 is positioned centrally within the cavity and extends longitudinally from a base of the cavity.

In this embodiment, the heating sheet 108 comprises a substrate and an electrically resistive track located on the substrate. The battery 104 is coupled to the heating sheet 108 to allow a current to pass through the electrically resistive track and heat the electrically resistive track and the heating sheet 108 to an operating temperature.

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

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

The user taking a puff from article 10 causes air to flow through the air inlet of the device. The puff detection mechanism detects that the air flow rate through the air inlet has increased to a threshold flow rate greater than zero. The puff detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 to pass a current through the electrically resistive track and heat the heating sheet 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. As such, these particles can act as local hot spots and provide a more uniform temperature throughout the aerosol-forming substrate, particularly in a radial direction from the heating sheet 108 where, with prior art substrates, there would be a significant temperature gradient. Furthermore, because the aerosol-forming substrate is tube-shaped, the temperature equalizes relatively quickly between the inner surface of the tube and the outer surface of the tube. The combination of a tubular structure for the aerosol-forming substrate and the presence of thermally conductive particles in the aerosol-forming substrate allows a greater proportion of the aerosol-forming substrate to quickly reach a temperature high enough to release volatile compounds, and therefore allows for greater 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 air flowing from the upstream end 18 of the article 10 to the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the cardboard tube 34. The aerosol then passes through the mouthpiece member 42, which can filter out unwanted particles entrained in the airflow, and into the user's mouth.

When the user stops inhaling through the device 10, the airflow rate through the device's air inlet decreases to less than the non-zero flow threshold. This is detected by the puff detection mechanism. The puff detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 to reduce the current passing through the electrically resistive track to zero.

After several puffs of Item 10, the user may choose to replace Item 10 with a new item.

Figure 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 Figure 1.

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

The aerosol generating device 302 further comprises a housing 310 defining an essentially cylindrical cavity for receiving a portion of the article 10. The external heater 208 is located on an internal surface of the cavity.

The use of the system is similar to that described above in relation to the system of Figure 2, with the difference that the tubular aerosol-forming substrate 12 is heated from the outside instead of by a heater located in an internal portion of the aerosol-forming substrate.

Figure 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 Figure 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 puff detection mechanism.

The aerosol generating device 402 further comprises a housing 410 defining an essentially cylindrical cavity for receiving a portion of the article 10. The inductor coil 408 is wound around the cavity.

The battery 404 is coupled to the inductor coil 408 so that an alternating current can be passed through the inductor coil 408.

In use, a user inserts the article 10 into the cavity. Figure 4 shows the article 10 inserted into the cavity of the device 402. Airflow is detected and the device is actuated as described above in connection with the system of Figure 1. When a puff is detected, the controller 406 controls the battery 404 to pass an alternating current through the inductor coil 408. This causes the inductor coil 408 to generate a fluctuating electromagnetic field. The aerosol-forming substrate 12 is located within this fluctuating electromagnetic field. The materials of the particles 44, for example graphite or expanded graphite, are susceptor materials. Therefore, the fluctuating electromagnetic field causes 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 description and the appended claims, except where otherwise indicated, all numbers expressing quantities, figures, percentages, etc., are to be understood as modified in all instances by the term "approximately." Furthermore, all ranges include the maximum and minimum points described and include any intermediate intervals therein, which may or may not be specifically enumerated in the present description. In this context, therefore, a number A is understood to mean A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within the general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above so long as the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Furthermore, all ranges include the maximum and minimum points described and include any intermediate ranges therein, which may or may not be specifically listed in this description.

Claims (15)

1. An aerosol-generating article (10) for producing an inhalable aerosol upon heating, the aerosol-generating article comprising a plurality of components including an aerosol-forming substrate (12), wherein: the aerosol-forming substrate is in the form of a hollow tubular segment defining a substrate cavity extending between an upstream end (18) of the aerosol-forming substrate and a downstream end (20) of the aerosol-forming substrate, the aerosol-forming substrate comprises a plurality of thermally conductive particles (44) and an aerosol former, each of the plurality of thermally conductive particles has a thermal conductivity greater than 0.3 W/(mK) in at least one direction at 25 degrees Celsius, and The substrate is in the form of a tube having an external diameter and an internal diameter, the internal diameter being between 2.5 mm and 19 mm. 2. An aerosol-generating article (10) according to claim 1 wherein the aerosol-forming substrate (12) comprises, on a dry weight basis: between 5 and 95% by weight, for example between 10 and 90% by weight, of thermally conductive particles (44), each thermally conductive particle of the thermally conductive particles having a thermal conductivity of at least 1 W/(mK) in at least one direction at 25 degrees Celsius. 3. An aerosol-generating article (10) according to claim 1 or 2, wherein the aerosol-forming substrate (12) has a thermal conductivity of at least 0.12 W/(mK) in at least one direction at 25 °C. 4. An aerosol-generating article (10) according to any preceding claim in which each of the thermally conductive particles (44) consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, carbon, and diamond. 5. An aerosol-generating article (10) according to any preceding claim wherein the aerosol-forming substrate (12) comprises, on a dry weight basis: between 10 and 90% by weight of thermally conductive particles (44); between 7 and 60% by weight of an aerosol former; between 2 and 20% by weight of fibers; and between 2 and 10% by weight of a binder, wherein each of the thermally conductive particles consists of one or more of graphite, expanded graphite, graphene, carbon nanotubes, carbon, and diamond. 6. An aerosol-generating article (10) according to any preceding claim, wherein the thermally conductive particles (44) are distributed essentially homogeneously throughout the aerosol-forming substrate (12). 7. An aerosol-generating article (10) according to any preceding claim, wherein the aerosol-forming substrate (12) comprises one or more organic materials such as tobacco. 8. An aerosol-generating article (10) according to any one of claims 1 to 6, wherein the aerosol-forming substrate (12) is a tobacco-free aerosol-forming substrate. 9. An aerosol-generating article (10) according to any preceding claim wherein a length of the tube is between 5 mm and 100 mm, and the external diameter is between 3 mm and 20 mm. 10. An aerosol-generating article (10) according to claim 9 wherein the length of the tube is between 8 mm and 25 mm, the external diameter of the tube is between 6 mm and 8 mm, and the internal diameter of the tube is between 5 mm and 7.9 mm. 11. An aerosol-generating article (10) according to any preceding claim wherein the hollow tubular segment is a rolled sheet of aerosol-forming material, for example a rolled sheet of homogenized tobacco material or, for example, a rolled sheet of tobacco-free aerosol-forming material. 12. An aerosol-generating article (10) according to any one of claims 1 to 10 wherein the hollow tubular segment is an extruded tube of aerosol-forming material, for example, an extruded tube of homogenized tobacco material or, for example, an extruded tube of tobacco-free aerosol-forming material. 13. A method for forming a hollow tubular aerosol-forming substrate (12) for an aerosol-generating article (10), for example, an aerosol-generating article as defined in any one of claims 1 to 12, the method comprising: forming a suspension comprising thermally conductive particles (44), an aerosol former, fibers and a binder, each of the thermally conductive particles having a thermal conductivity greater than 0.3 W/(mK) in at least one direction at 25 degrees Celsius; molding and drying the suspension to form a sheet of aerosol-forming material, and forming the sheet into a hollow tube, the hollow tube having an outer diameter and an inner diameter, the inner diameter being between 2.5 mm and 19 mm. 14. A method according to claim 13, wherein forming the suspension comprises: form a first mixture comprising: the aerosol former; the fibers; water; optionally, an acid; and optionally, nicotine, form a second mixture comprising: thermally conductive particles (44); and the binder, and add the second mixture to the first mixture to form a combined mixture. 15. An aerosol-generating system (100) comprising an aerosol-generating article (10) according to any one of claims 1 to 12 and an electric aerosol-generating device (102), preferably wherein the electric aerosol-generating device is configured to resistively heat the aerosol-generating article during use, or wherein the electric aerosol-generating device is configured to inductively heat the aerosol-generating article, for example, the aerosol-forming substrate (12) of the aerosol-generating article, during use.