EP4654844A1

EP4654844A1 - Aerosol-generating article with low resistance to draw

Info

Publication number: EP4654844A1
Application number: EP24701700.7A
Authority: EP
Inventors: Farhang MOHSENI; Paola ORSOLINI
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2023-01-25
Filing date: 2024-01-24
Publication date: 2025-12-03
Also published as: KR20250131834A; WO2024156765A1; MX2025008406A; CN120897680A

Abstract

There is provided an aerosol-generating article (10) for producing an inhalable aerosol upon heating, the aerosol-generating article (10) extending from a downstream end (20) to an upstream end (18) and comprising: an aerosol-generating section (52) comprising a rod of aerosol-generating substrate (12); a mouthpiece section (46) comprising a mouthpiece filter segment (42) formed of a fibrous filtration material; and an intermediate hollow section (50) defining a longitudinal cavity providing an unrestricted flow channel from the aerosol-generating section (52) to the mouthpiece section (64). The mouthpiece section has a length L1 extending between the upstream end (62) of the mouthpiece filter segment (42) and the downstream end (20) of the aerosol-generating article. The intermediate hollow section (50) has a length L2 extending between the downstream end of the aerosol-generating section (52) and the upstream end of the mouthpiece section. The intermediate hollow section (50) comprises: an aerosol-cooling segment (24) downstream of the aerosol-generating section (52) and a support segment (22) between the aerosol-cooling segment (24) and the aerosol-generating section (52). The length (L1) of the mouthpiece section (46) is at least 0.10 times and less than 0.34 times the length (L2) of the intermediate hollow section (50).

Description

AEROSOL-GENERATING ARTICLE WITH LOW RESISTANCE TO DRAW

The present invention relates to an aerosol-generating article comprising an aerosolgenerating substrate and adapted to produce an inhalable aerosol upon heating.

Aerosol-generating articles in which an aerosol-generating substrate, such as a tobaccocontaining substrate, is heated rather than combusted, are known in the art. Typically, in such heated smoking articles an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, 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 air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

Consumables, in which a solid substrate in the form of a gel or film containing nicotine, that are heated rather than combusted, are known in the art. By way of example, WO 2018/019543 discloses a thermoreversible gel composition, that is, a gel that will become fluid when heated to a melting temperature and will set into a gel again at a gelation temperature. The gel is provided within a housing of a cartridge, and the cartridge can be disposed of and replaced when the gel has been consumed. WO 2020/207733 discloses a consumable comprising a rod of aerosol-generating substrate with a plurality of stacked layers of an aerosol-generating film. In use, the majority of the components of the film may evaporate on heating, leaving minimal residue and allowing for an article that is easier to dispose of and has a reduced environmental impact.

A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosolgenerating devices in which an aerosol is generated by the transfer of heat from one or more electrical heater 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 that comprise an internal heater blade which is adapted to be inserted into the aerosol-generating substrate. As an alternative, inductively heatable aerosol-generating articles comprising an aerosol-generating substrate and a susceptor arranged within the aerosolgenerating substrate have been proposed by WO 2015/176898. A further alternative has been described in WO 2020/115151 , which discloses an aerosol-generating article used in combination with an external heating system comprising one or more heating elements arranged around the periphery of the aerosol-generating article. For example, external heating elements may be provided in the form of flexible heating foils on a dielectric substrate, such as polyimide. External heating could be resistive or inductive.

Aerosol-generating articles in which a tobacco-containing substrate is heated rather than combusted present a number of challenges that were not encountered with conventional smoking articles. First of all, tobacco-containing substrates are typically heated to significantly lower temperatures compared with the temperatures reached by the combustion front in a conventional cigarette. This may have an impact on nicotine release from the tobacco-containing substrate and nicotine delivery to the consumer. At the same time, if the heating temperature is increased in an attempt to boost nicotine delivery, then the aerosol generated typically needs to be cooled to a greater extent and more rapidly before it reaches the consumer. However, technical solutions that were commonly used for cooling the mainstream smoke in conventional smoking articles, such as the provision of a high filtration efficiency segment at the mouth end of a cigarette, may have undesirable effects in an aerosol-generating article wherein a tobacco-containing substrate is heated rather than combusted, as they may reduce nicotine delivery.

In order to address one or more of the challenges specifically associated with heating rather than combusting an aerosol-generating substrate to generate an aerosol, a number of aerosol-generating articles have been proposed wherein multiple elements are combined, for example in longitudinal alignment, with an aerosol-generating element containing the aerosolgenerating substrate. By way of example, the aerosol-generating element has been combined with a support element to impart improved structural strength to the article, an aerosol-cooling element adapted to lower the temperature of the aerosol, a low-filtration mouthpiece element, etc.

A need is generally felt for aerosol-generating articles that are easy to use and have improved practicality. Additionally, it would be desirable to provide aerosol-generating articles that are easier to manufacture and that may make the whole production chain more sustainable and cost-effective. There is also a need for an aerosol-generating article that is especially suitable for use in combination with an external heating system, and particularly one that has improved aerosol generation and aerosol former delivery. There is further a need to provide such an aerosol-generating article that is easier to dispose of after use or that has reduced environmental impact.

Heating of substrates comprising cellulose based material, in particular hydroxypropylmethyl cellulose (HPMC), to temperatures which are too high, such as higher than 300 degrees Celsius, can lead to a paper off-taste and the generation of formaldehyde. However, heating such substrates to lower temperatures, while reducing the levels of harmful and potentially harmful compounds (HPHCs) generated, also reduces the aerosolization of the aerosol former and nicotine. Additionally, compared to gel substrates which can comprise a relatively high quantity by weight of aerosol former, film substrates comprise a relatively high quantity by weight of cellulose based material to impart structure to the film along with a lower quantity by weight of aerosol former. The lower quantity by weight of aerosol former used in film substrates also reduces the efficiency of delivery of aerosol former and nicotine relative to gel substrates. There is a need to provide an aerosol-generating article comprising a film substrate that allows for efficient delivery of aerosol-former, as well as nicotine. Therefore, it would be desirable to provide a new and improved aerosol-generating article adapted to satisfy at least one of the needs described above. Further, it would be desirable to provide an aerosol-generating article that allows for efficient delivery of nicotine and/or aerosol former, like glycerine, while maintaining low levels or even reducing levels of HPHCs. Further, it would be desirable to provide one such aerosol-generating article that can be manufactured efficiently and at high speed, preferably with a satisfactory low RTD variability from one article to another.

The present disclosure relates to an aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article extending from an upstream end to a downstream end. The aerosol-generating article comprises an aerosol-generating section comprising a rod of aerosol-generating substrate. The aerosol-generating article may further comprise a mouthpiece section comprising a mouthpiece filter segment formed of a fibrous filtration material, the mouthpiece section having a length L1 extending between the upstream end of the mouthpiece filter segment and the downstream end of the aerosol-generating article. The aerosol-generating article may comprise an intermediate hollow section having a length L2 extending between the aerosol-generating section and the mouthpiece section, the intermediate hollow section defining a longitudinal cavity providing an unrestricted flow channel from the aerosol-generating section to the mouthpiece section. The intermediate hollow section may comprise an aerosol-cooling segment downstream of the aerosol-generating section. The intermediate hollow section may further comprise a support segment between the aerosol-cooling segment and the aerosol-generating section. The length of the mouthpiece section (L1) may be at least 0.10 times and less than 0.40 times the length of the intermediate hollow section (L2).

According to the present invention there is provided an aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article extending from an upstream end to a downstream end and comprising: an aerosol-generating section comprising a rod of aerosol-generating substrate; a mouthpiece section comprising a mouthpiece filter segment formed of a fibrous filtration material, the mouthpiece section having a length L1 extending between the upstream end of the mouthpiece filter segment and the downstream end of the aerosol-generating article; an intermediate hollow section having a length L2 extending between the aerosol-generating section and the mouthpiece section, the intermediate hollow section defining a longitudinal cavity providing an unrestricted flow channel from the aerosolgenerating section to the mouthpiece section. The intermediate hollow section comprises: an aerosol-cooling segment downstream of the aerosol-generating section; and a support segment between the aerosol-cooling segment and the aerosol-generating section. According to the invention, the length of the mouthpiece section (L1) is at least 0.10 times and less than 0.40 times the length of the intermediate hollow section (L2). In accordance with the present invention there is provided an aerosol-generating article for generating an inhalable aerosol upon heating. The aerosol-generating article consists of three sections: an aerosol-generating section, an intermediate hollow section downstream of the aerosol-generating section, and a mouthpiece section downstream of the intermediate hollow section. The aerosol-generating article comprises an aerosol-generating section comprising a rod of aerosol-generating substrate.

The term “aerosol-generating article” is used herein to denote an article wherein an aerosol-generating substrate is heated to produce and deliver an inhalable aerosol to a consumer. As used herein, the term “aerosol-generating substrate” denotes a substrate capable of releasing volatile compounds upon heating to generate an aerosol.

The aerosol-generating articles of the present invention optionally comprise aerosolgenerating films. Such substrates are designed to be heated to relatively low temperatures, that is to say, temperatures less than approximately 300 degrees Celsius, to minimise levels of formaldehyde generated and to avoid paper off-taste. Although heating substrates such as aerosol-generating films to lower temperatures reduces the levels of HPHCs generated, it also reduces the aerosolization of the aerosol former and nicotine. Additionally, relative to gel substrates, aerosol-generating films comprise a relatively high quantity by weight of cellulose- based material to impart structure to the film along with a lower quantity by weight of aerosol former. The lower quantity by weight of aerosol former reduces the efficiency of delivery of aerosol former and nicotine in film substrates relative to gel substrates. The aerosol-generating articles of the present invention optionally comprising aerosol-generating film substrates allow for efficient delivery of aerosol former as well as nicotine to the consumer by virtue of their relatively lower filtration and low RTD of the downstream section comprising the intermediate hollow section and the mouthpiece section, compared to conventional aerosol-generating articles.

A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. The localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke. By contrast, in heated aerosol-generating articles, an aerosol is generated by heating a flavour generating substrate, such as tobacco. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol forming material. For example, aerosol-generating articles find particular application in aerosol-generating systems comprising an electrically heated aerosol-generating device having an internal heater blade which is adapted to be inserted into the rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example, in EP 0822670. As used herein, the term “aerosol-generating device” refers to a device comprising a heater element that interacts with the aerosol-generating substrate of the aerosol-generating article to generate an aerosol. During use, volatile compounds are released from the aerosol-generating substrate by heat transfer and entrained in air drawn through the aerosol-generating article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.

The aerosol-generating element may be in the form of a rod comprising or made of the aerosol-generating substrate. As used herein with reference to the present invention, the term “rod” is used to denote a generally cylindrical element of substantially circular, oval or elliptical cross-section.

As used herein, the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article. As used herein, the terms “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosolgenerating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use.

As used herein, the term “upstream end of the aerosol-generating article” refers to the distal end of the aerosol-generating article.

As used herein, the term “downstream end of the aerosol-generating article” refers to the mouth end of the aerosol-generating article.

During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term “transverse” refers to the direction that is perpendicular to the longitudinal axis. Any reference to the “cross-section” of the aerosol-generating article or a component of the aerosolgenerating article refers to the transverse cross-section unless stated otherwise.

The term “length” denotes the dimension of a component of the aerosol-generating article in the longitudinal direction. For example, it may be used to denote the dimension of the rod or of the elongate tubular elements in the longitudinal direction.

Unless otherwise specified, the resistance to draw (RTD) of a component or the aerosolgenerating article is measured in accordance with ISO 6565-2015. The RTD refers the pressure required to force air through the full length of a component. The terms “pressure drop” or “draw resistance” of a component or article may also refer to the “resistance to draw”. Such terms generally refer to the measurements in accordance with ISO 6565-2015 are normally carried out at under test at a volumetric flow rate of about 17.5 millilitres per second at the output or downstream end of the measured component at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr) and a relative humidity of about 60%.

The aerosol-generating article according to the present invention provides an improved configuration of the elements downstream of the aerosol-generating section, which is defined by having a ratio of the length of the mouthpiece section to the length of the intermediate hollow section of at least 0.10 times and less than 0.40 times. This ratio reflects a configuration in which a relatively short mouthpiece section is provided in combination with a longer intermediate hollow section than has been previously provided. In particularly preferred embodiments of the present invention, the improved configuration provides a relatively short mouthpiece section in combination with a longer aerosol-cooling segment than has been previously provided.

By increasing the distance between the aerosol-generating section and the mouthpiece section whilst at the same time decreasing the length of the mouthpiece section it has been found to be possible to provide a product that has a lower resistance to draw (RTD) of the mouthpiece section. This allows for improved aerosol delivery and efficient nicotine and glycerine delivery while maintaining low levels or even reducing levels of HPHCs. Moreover, a shorter mouthpiece section allows for improved product sustainability, as lower amounts of plasticisers are used in manufacturing the mouthpiece section. Advantageously, these benefits can be provided without affecting the overall length of the article, such that a total length that is consistent with existing aerosol-generating articles can be maintained.

An increase in the length of the intermediate hollow section relative to the mouthpiece section may advantageously be provided by increasing the length of the aerosol-cooling segment, as described in more detail below.

In accordance with the present invention there is provided an aerosol-generating article for generating an inhalable aerosol upon heating.

The aerosol-generating article comprises an aerosol-generating section comprising a rod of aerosol-generating substrate. The aerosol-generating section may further comprise one or more upstream segments, at a location upstream of the rod of aerosol-generating substrate. In some embodiments, the aerosol-generating section may further comprise an upstream segment arranged immediately upstream of the rod of aerosol-generating substrate. The aerosolgenerating section may further comprise one or more segments that are not hollow and abut with the rod of aerosol-generating substrate to form a continuous non-hollow section. For example, a filter segment formed of a fibrous filtration material and abutting the rod of aerosol-generating substrate may be part of the aerosol-generating section. Such non-hollow segments may abut the rod of aerosol-generating substrate at a location that is upstream or downstream of the rod of aerosol-generating substrate.

The aerosol-generating section extends from the upstream end of the aerosol-generating article to the downstream end of either the rod of aerosol-generating substrate or the downstream end of any non-hollow segment that abuts with the rod of aerosol-generating substrate to form a continuous non-hollow section, downstream of the rod of aerosol-generating substrate.

The aerosol-generating article further comprises a downstream section at a location downstream of the aerosol-generating section. The downstream section comprises an intermediate hollow section and a mouthpiece section. In the aerosol-generating article according to the present invention, the mouthpiece section comprises a mouthpiece filter segment. The mouthpiece section extends from the upstream end of the mouthpiece filter segment to the downstream end of the aerosol-generating article.

The downstream section further comprises an intermediate hollow section between the mouthpiece section and the aerosol-generating section. The intermediate hollow section (50) has a length L2 extending between the downstream end of the aerosol-generating section (52) and the upstream end of the mouthpiece section. The intermediate hollow section comprises a support segment and an aerosol-cooling segment. The aerosol-cooling segment comprises a hollow tubular segment. The support segment may also comprise a hollow tubular segment.

As used herein, the term "hollow tubular segment" is denotes a generally elongate element defining a lumen or airflow passage along a longitudinal axis thereof. In particular, the term "tubular" will be used in the following with reference to a tubular segment having a substantially cylindrical cross-section and defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the tubular segment and a downstream end of the tubular segment. However, it will be understood that alternative geometries (for example, alternative cross-sectional shapes) of the tubular segment may be possible.

As used herein, the term “elongate” means that an element has a length dimension that is greater than its width dimension or its diameter dimension, for example twice or more its width dimension or its diameter dimension.

In the context of the present invention a hollow tubular segment provides an unrestricted flow channel. This means that the hollow tubular segment provides a negligible level of resistance to draw (RTD). The flow channel should therefore be free from any components that would obstruct the flow of air in a longitudinal direction. Preferably, the flow channel is substantially empty.

In some embodiments, the aerosol-generating article may comprise a ventilation zone at a location along the intermediate hollow section. In more detail, the aerosol-generating article may comprise a ventilation zone at a location along the aerosol-cooling segment. In preferred embodiments, the aerosol-cooling segment comprises or is in the form of a hollow tubular segment, the ventilation zone being provided at a location along the hollow tubular segment of the aerosol-cooling element.

The aerosol-generating article may further comprise a susceptor element within the aerosol-generating substrate. In some embodiments, the susceptor element may be an elongate susceptor element. In preferred embodiments, the susceptor element extends longitudinally within the aerosol-generating substrate.

These elements of the aerosol-generating article will be described in further detail below. As defined above, the mouthpiece section of the aerosol-generating article of the present invention comprises a mouthpiece filter segment. In certain embodiments of the invention, the mouthpiece section may comprise a mouth end cavity at the downstream end of the mouthpiece section, downstream of the mouthpiece filter segment. The mouthpiece section may comprise a mouth end cavity at the downstream end of the aerosol-generating article.

The mouthpiece filter segment is preferably located at the downstream end of the aerosolgenerating article. The mouthpiece filter segment comprises a fibrous filtration material for filtering the aerosol that is generated from the aerosol-generating substrate. Suitable fibrous filtration materials would be known to the skilled person. Particularly preferably, the at least one mouthpiece filter segment comprises a cellulose acetate filter segment formed of cellulose acetate tow.

In certain preferred embodiments, the mouthpiece section consists of a single mouthpiece filter segment. In alternative embodiments, the mouthpiece section includes two or more mouthpiece filter segments axially aligned in an abutting end to end relationship with each other.

In certain embodiments of the invention, the mouthpiece section may comprise a mouth end cavity at the downstream end, downstream of the mouthpiece filter segment as described above. The mouth end cavity may be defined by a hollow tubular segment provided at the downstream end of the mouthpiece section. Alternatively, the mouth end cavity may be defined by the outer wrapper of the mouthpiece section, wherein the outer wrapper extends in a downstream direction from the mouthpiece filter segment.

The mouthpiece filter segment may optionally comprise a flavourant, which may be provided in any suitable form. For example, the mouthpiece filter segment may comprise one or more capsules, beads or granules of a flavourant, or one or more flavour loaded threads or filaments.

According to the present invention, the intermediate hollow section of the aerosolgenerating article further comprises a support segment located immediately downstream of the aerosol-generating section. Preferably, the support segment is located immediately downstream of the rod of aerosol-generating substrate. The mouthpiece section is preferably located downstream of the support segment. The intermediate hollow section further comprises an aerosol-cooling segment located immediately downstream of the support segment. The mouthpiece section is preferably located downstream of both the support segment and the aerosol-cooling segment. Particularly preferably, the mouthpiece section is located immediately downstream of the aerosol-cooling segment. By way of example, the mouthpiece filter segment may abut the downstream end of the aerosol-cooling segment.

Preferably, the mouthpiece filter segment has a low particulate filtration efficiency. Preferably, the mouthpiece section is circumscribed by a plug wrap. Preferably, the mouthpiece section is unventilated such that air does not enter the aerosol-generating article along the mouthpiece section.

The mouthpiece section is preferably connected to one or more of the adjacent upstream components of the aerosol-generating article by means of a tipping wrapper.

Preferably, the mouthpiece section has an RTD of less than about 10 millimetres H2O. More preferably, the mouthpiece section has an RTD of less than about 9 millimetres H2O. Even more preferably, the mouthpiece section has an RTD of less than about 8 millimetres H2O.

Preferably, the mouthpiece section has an RTD of at least about 1 millimetre H2O. More preferably, the mouthpiece section has an RTD of at least about 2 millimetres H2O. Even more preferably, the mouthpiece section has an RTD of at least about 5 millimetres H2O.

Values of RTD from about 1 millimetre H2O to about to about 10 millimetres H2O are particularly preferred because a mouthpiece section having one such RTD is expected to contribute minimally to the overall RTD of the aerosol-generating article substantially does not exert a filtration action on the aerosol being delivered to the consumer.

In a preferred embodiment, the mouthpiece section consists of a single mouthpiece filter segment. Preferably, the mouthpiece filter segment has an RTD of less than about 10 millimetres H2O. More preferably, the mouthpiece filter segment has an RTD of less than about 9 millimetres H2O. Even more preferably, the mouthpiece filter segment has an RTD of less than about 8 millimetres H2O.

Preferably, the mouthpiece filter segment has an RTD of at least about 1 millimetre H2O. More preferably, the mouthpiece filter segment has an RTD of at least about 2 millimetres H2O. Even more preferably, the mouthpiece filter segment has an RTD of at least about 5 millimetres H₂O.

Values of RTD from about 1 millimetre H2O to about to about 10 millimetres H2O are particularly preferred because a mouthpiece filter segment having one such RTD is expected to contribute minimally to the overall RTD of the aerosol-generating article substantially does not exert a filtration action on the aerosol being delivered to the consumer.

The mouthpiece section preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. The mouthpiece section may have an external diameter of between about 5 millimetres and about 10 millimetres, or between about 6 millimetres and about 8 millimetres. In a preferred embodiment, the mouthpiece section has an external diameter of approximately 7.2 millimetres.

In some embodiments, the mouthpiece section preferably has a length from about 1 millimetre to about 10 millimetres, more preferably from about 3 millimetres to about 9 millimetres, even more preferably from about 5 millimetres to about 9 millimetres. For example, the mouthpiece section may have a length of between about 1 millimetre and about 10 millimetres, or between about 3 millimetres and about 9 millimetres, or between about 5 millimetres and about 9 millimetres. In a preferred embodiment, the mouthpiece section has a length of approximately 7 millimetres.

In certain preferred embodiments of the invention, the mouthpiece section has a length of at most 10 millimetres, or less than 10 millimetres. In such embodiments, the mouthpiece section is therefore relatively short compared to the mouthpiece section provided in prior art articles. The provision of a relatively short mouthpiece section in the aerosol-generating articles of the present invention may provide several benefits to the consumer. A shorter mouthpiece section allows for a lower resistance to draw (RTD) of the mouthpiece section. This allows for improved aerosol delivery and efficient delivery of nicotine and/or aerosol former, like glycerine, while maintaining low levels or even reducing levels of HPHCs. Moreover, a shorter mouthpiece section allows for improved product sustainability, as lower amounts of plasticisers are used in manufacturing the mouthpiece element.

In particularly preferred embodiments of the invention, a mouthpiece section having a length of at most 10 millimetres or less than 10 millimetres is combined with a relatively short aerosolcooling segment, for example, an aerosol-cooling segment having a length of at least 10 millimetres. This combination has been found to provide a satisfactory delivery of aerosol, particularly of nicotine and glycerine, while maintaining low levels or even reducing levels of HPHCs.

In accordance with the present invention, the length of the mouthpiece section is at least about 0.10 times the length of the intermediate hollow section, preferably at least about 0.15 times the length of the intermediate hollow section, more preferably at least about 0.20 times the length of the intermediate hollow section, even more preferably at least about 0.25 times the length of the intermediate hollow section, and most preferably at least 0.30 times the length of the intermediate hollow section. The ratio between the length of the mouthpiece section and the length of the intermediate hollow section is therefore at least about 0.10, preferably at least about 0.15, more preferably at least about 0.20, even more preferably at least about 0.25, and most preferably at least about 0.30.

In accordance with the present invention, the length of the mouthpiece section is less than about 0.40 times the total length of the intermediate hollow section, preferably less than about 0.38 times the length of the intermediate hollow section, more preferably less than about 0.36 times the length of the intermediate hollow section, most preferably less than about 0.34 times the length of the intermediate hollow section. The ratio between the length of the mouthpiece section and the length of the intermediate hollow section is therefore less than about 0.40, preferably less than about 0.38, more preferably less than about 0.36 and most preferably less than about 0.34. A ratio between the length of the mouthpiece section and the length of the intermediate hollow section may be at least about 0.10 and less than about 0.40, preferably at least about 0.10 and less than about 0.38, more preferably at least about 0.10 and less than 0.36, and even more preferably at least about 0.10 and less than 0.34. A ratio between the length of the mouthpiece section and the length of the intermediate hollow section may be at least about 0.15 and less than 0.40, preferably at least about 0.15 and less than about 0.38, more preferably at least about 0.15 and less than 0.36, and even more preferably at least about 0.15 and less than about 0.34. A ratio between the length of the mouthpiece section and the length of the intermediate hollow section may be at least about 0.20 and less than about 0.40, preferably at least about 0.20 and less than about 0.38, more preferably at least about 0.20 and less than 0.36, and even more preferably at least about 0.20 and less than 0.34. A ratio between the length of the mouthpiece section and the length of the intermediate hollow section may be at least about 0.25 and less than about 0.40, preferably at least about 0.25 and less than about 0.38, more preferably at least about 0.25 and less than 0.36, and even more preferably at least about 0.25 and less than 0.34. A ratio between the length of the mouthpiece section and the length of the intermediate hollow section may be at least about 0.30 and less than about 0.40, preferably at least about 0.30 and less than about 0.38, more preferably at least about 0.30 and less than 0.36, and even more preferably at least about 0.30 and less than 0.34.

A ratio between the length of the mouthpiece section and the length of the rod of aerosolgenerating substrate may be from about 0.10 to less than about 0.60.

Preferably, a ratio between the length of the mouthpiece section and the length of the rod of aerosol-generating substrate is at least about 0.10, more preferably at least about 0.20, even more preferably at least about 0.30. In preferred embodiments, a ratio between the length of the mouthpiece section and the length of the rod of aerosol-generating substrate is less than about 0.60.

In some embodiments, a ratio between the length of the mouthpiece section and the length of the rod of aerosol-generating substrate is from about 0.10 to less than about 0.60, preferably from about 0.20 to less than about 0.60, more preferably from about 0.30 to less than about 0.60.

In a particularly preferred embodiment, a ratio between the length of the mouthpiece section and the length of the rod of aerosol-generating substrate is about 0.58.

Preferably, a ratio between the length of the mouthpiece section and the length of the aerosol-generating section is at least about 0.10, more preferably at least about 0.20, even more preferably at least about 0.30. In preferred embodiments, a ratio between the length of the mouthpiece section and the length of the aerosol-generating section is less than about 0.60.

In some embodiments, a ratio between the length of the mouthpiece section and the length aerosol-generating section is from about 0.10 to less than about 0.60, preferably from about 0.20 to less than about 0.60, more preferably from about 0.30 to less than about 0.60. In a particularly preferred embodiment, a ratio between the length of the mouthpiece section and the length of the aerosol-generating section is about 0.41 .

A ratio between the length of the mouthpiece section and the overall length of the aerosolgenerating article may be from about 0.01 to less than about 0.20.

Preferably, a ratio between the length of the mouthpiece section and the overall length of the aerosol-generating article is at least about 0.05, more preferably at least about 0.07, even more preferably at least about 0.10. A ratio between the length of the mouthpiece section and the overall length of the aerosol-generating article is preferably less than about 0.20.

In some embodiments, a ratio between the length of the mouthpiece section and the overall length of the aerosol-generating article is preferably from about 0.05 to less than about 0.20, more preferably from about 0.07 to less than about 0.20, even more preferably from about 0.10 to less than about 0.20.

In a particularly preferred embodiment, a ratio between the length of the mouthpiece section and the overall length of the aerosol-generating article is about 0.16.

In a preferred embodiment, the mouthpiece section consists of a single mouthpiece filter segment. The mouthpiece filter segment preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article. The mouthpiece filter segment may have an external diameter of between about 5 millimetres and about 10 millimetres, or between about 6 millimetres and about 8 millimetres. In a preferred embodiment, the mouthpiece filter segment has an external diameter of approximately 7.2 millimetres.

In some embodiments, the mouthpiece filter segment preferably has a length from about 1 millimetre to about 10 millimetres, more preferably from about 3 millimetres to about 9 millimetres, even more preferably from about 5 millimetres to about 9 millimetres.

For example, the mouthpiece filter segment may have a length of between about 1 millimetre and about 10 millimetres, or between about 3 millimetres and about 9 millimetres, or between about 5 millimetres and about 9 millimetres. In a preferred embodiment, the mouthpiece filter segment has a length of approximately 7 millimetres.

In certain preferred embodiments of the invention, the mouthpiece filter segment has a length of at most 10 millimetres, or less than 10 millimetres. In such embodiments, the mouthpiece filter segment is therefore relatively short compared to the mouthpiece filter segment provided in prior art articles. The provision of a relatively short mouthpiece filter segment in the aerosol-generating articles of the present invention may provide several benefits to the consumer. A shorter mouthpiece filter segment allows for a lower resistance to draw (RTD) of the mouthpiece filter segment. This allows for improved aerosol delivery and efficient delivery of nicotine and/or aerosol former, like glycerine, while maintaining low levels or even reducing levels of HPHCs. Moreover, a shorter mouthpiece filter segment allows for improved product sustainability, as lower amounts of plasticisers are used in manufacturing the mouthpiece filter segment. In particularly preferred embodiments of the invention, a mouthpiece filter segment having a length of at most 10 millimetres or less than 10 millimetres is combined with a relatively short aerosol-cooling segment, for example, an aerosol-cooling segment having a length of at least 10 millimetres. This combination has been found to provide a satisfactory delivery of aerosol, particularly of nicotine and glycerine, while maintaining low levels or even reducing levels of HPHCs.

The mouthpiece filter segment may have a length that is at least about 0.10 times the length of the intermediate hollow section, more preferably at least about 0.15 times the length of the intermediate hollow section, more preferably at least about 0.20 times the length of the intermediate hollow section, more preferably at least about 0.25 times the length of the intermediate hollow section, and more preferably at least 0.30 times the length of the intermediate hollow section.

The length of the mouthpiece filter segment may be less than 0.40 times the total length of the intermediate hollow section, preferably less than 0.38 times the length of the intermediate hollow section, more preferably less than 0.36 times the length of the intermediate hollow section, more preferably less than 0.34 times the length of the intermediate hollow section. The ratio between the length of the mouthpiece filter segment and the total length of the intermediate hollow section is therefore less than about 0.40, preferably less than about 0.38, more preferably less than about 0.36 and most preferably less than about 0.34.

A ratio between the length of the mouthpiece filter segment and the length of the intermediate hollow section may be at least about 0.10 and less than about 0.40, preferably at least about 0.10 and less than about 0.38, more preferably at least about 0.10 and less than 0.36, and even more preferably at least about 0.10 and less than 0.34. A ratio between the length of the mouthpiece filter segment and the length of the intermediate hollow section may be at least about 0.15 and less than 0.40, preferably at least about 0.15 and less than about 0.38, more preferably at least about 0.15 and less than 0.36, and even more preferably at least about 0.15 and less than about 0.34. A ratio between the length of the mouthpiece filter segment and the length of the intermediate hollow section may be at least about 0.20 and less than about 0.40, preferably at least about 0.20 and less than about 0.38, more preferably at least about 0.20 and less than 0.36, and even more preferably at least about 0.20 and less than 0.34. A ratio between the length of the mouthpiece filter segment and the length of the intermediate hollow section may be at least about 0.25 and less than about 0.40, preferably at least about 0.25 and less than about 0.38, more preferably at least about 0.25 and less than 0.36, and even more preferably at least about 0.25 and less than 0.34. A ratio between the length of the mouthpiece filter segment and the length of the intermediate hollow section may be at least about 0.30 and less than about 0.40, preferably at least about 0.30 and less than about 0.38, more preferably at least about 0.30 and less than 0.36, and even more preferably at least about 0.30 and less than 0.34. A ratio between the length of the mouthpiece filter segment and the length of the rod of aerosol-generating substrate may be from about 0.10 to less than about 0.60.

Preferably, a ratio between the length of the mouthpiece filter segment and the length of the rod of aerosol-generating substrate is at least about 0.10, more preferably at least about 0.20, even more preferably at least about 0.30. In preferred embodiments, a ratio between the length of the mouthpiece filter segment and the length of the rod of aerosol-generating substrate is less than about 0.60.

In some embodiments, a ratio between the length of the mouthpiece filter segment and the length of the rod of aerosol-generating substrate is from about 0.10 to less than about 0.60, preferably from about 0.20 to less than about 0.60, more preferably from about 0.30 to less than about 0.60.

In a particularly preferred embodiments, a ratio between the length of the mouthpiece filter segment and the length of the rod of aerosol-generating substrate is about 0.58.

Preferably, a ratio between the length of the mouthpiece filter segment and the length of the aerosol-generating section is at least about 0.10, more preferably at least about 0.20, even more preferably at least about 0.30. In preferred embodiments, a ratio between the length of the mouthpiece filter segment and the length of the aerosol-generating section is less than about 0.60.

In some embodiments, a ratio between the length of the mouthpiece filter segment and the length aerosol-generating section is from about 0.10 to less than about 0.60, preferably from about 0.20 to less than about 0.60, more preferably from about 0.30 to less than about 0.60.

In a particularly preferred embodiment, a ratio between the length of the mouthpiece filter segment and the length of the aerosol-generating section is about 0.41 .

A ratio between the length of the mouthpiece filter segment and the overall length of the aerosol-generating article may be from about 0.01 to less than about 0.20.

Preferably, a ratio between the length of the mouthpiece filter segment and the overall length of the aerosol-generating article is at least about 0.05, more preferably at least about 0.07, even more preferably at least about 0.10. A ratio between the length of the mouthpiece filter segment and the overall length of the aerosol-generating article is preferably less than about 0.20.

In some embodiments, a ratio between the length of the mouthpiece filter segment and the overall length of the aerosol-generating article is preferably from about 0.05 to less than about 0.20, more preferably from about 0.07 to less than about 0.20, even more preferably from about 0.10 to less than about 0.20.

In a particularly preferred embodiment, a ratio between the length of the mouthpiece filter segment and the overall length of the aerosol-generating article is about 0.16.

As described above, the downstream section of the aerosol-generating articles in accordance with the present invention further comprises an intermediate hollow section comprising an aerosol-cooling segment arranged in alignment with, and downstream of the aerosol-generating section.

The aerosol-cooling segment is arranged substantially in alignment with the rod of aerosolgenerating substrate. This means that the length dimension of the aerosol-cooling segment is arranged to be approximately parallel to the longitudinal direction of the rod and of the article, for example within plus or minus 10 degrees of parallel to the longitudinal direction of the rod. In preferred embodiments, the aerosol-cooling segment extends along the longitudinal axis of the rod.

In aerosol-generating articles in accordance with the present invention the aerosol-cooling segment is in the form of a hollow tubular segment that defines a cavity extending all the way from an upstream end of the aerosol-cooling segment to a downstream end of the aerosol-cooling segment. Preferably, a ventilation zone is provided at a location along the hollow tubular segment.

The inventors have found that a satisfactory cooling of the stream of aerosol generated upon heating the aerosol-generating substrate and drawn through one such aerosol-cooling segment is achieved by providing a ventilation zone at a location along the hollow tubular segment. Further, the inventors have found that, as will be described in more detail below, by arranging the ventilation zone at a precisely defined location along the length of the aerosolcooling segment and by preferably utilising a hollow tubular segment having a predetermined peripheral wall thickness or internal volume, it may be possible to counter the effects of the increased aerosol dilution caused by the admission of ventilation air into the article.

Without wishing to be bound by theory, it is hypothesised that, because the temperature of the aerosol stream is rapidly lowered by the introduction of ventilation air as the aerosol is travelling towards the mouthpiece section, the ventilation air being admitted into the aerosol stream at a location relatively close to the upstream end of the aerosol-cooling segment (that is, sufficiently close to the susceptor element extending within the rod of aerosol-generating substrate, which is the heat source during use), a dramatic cooling of the aerosol stream is achieved, which has a favourable impact on the condensation and nucleation of the aerosol particles. Accordingly, the overall proportion of the aerosol particulate phase to the aerosol gas phase may be enhanced compared with existing, non-ventilated aerosol-generating articles.

At the same time, keeping the thickness of the peripheral wall of the hollow tubular segment relatively low ensures that the overall internal volume of the hollow tubular segment - which is made available for the aerosol to begin the nucleation process as soon as the aerosol components leave the rod of aerosol-generating substrate - and the cross-sectional surface area of the hollow tubular segment are effectively maximised, whilst at the same time ensuring that the hollow tubular segment has the necessary structural strength to prevent a collapse of the aerosolgenerating article as well as to provide some support to the rod of aerosol-generating substrate, and that the RTD of the hollow tubular segment is minimised. Greater values of cross-sectional surface area of the cavity of the hollow tubular segment are understood to be associated with a reduced speed of the aerosol stream travelling along the aerosol-generating article, which is also expected to favour aerosol nucleation. Further, it would appear that by utilising a hollow tubular segment having a relatively low thickness, it is possible to substantially prevent diffusion of the ventilation air prior to its contacting and mixing with the stream of aerosol, which is also understood to further favour nucleation phenomena. In practice, by providing a more controllably localised cooling of the stream of volatilised species, it is possible to enhance the effect of cooling on the formation of new aerosol particles.

The aerosol-cooling segment preferably has an outer diameter that is approximately equal to the outer diameter of the aerosol-generating section, to the rod of aerosol-generating substrate and to the outer diameter of the aerosol-generating article.

The aerosol-cooling segment may have an outer diameter of between 5 millimetres and 12 millimetres, for example of between 5 millimetres and 10 millimetres or of between 6 millimetres and 8 millimetres. In a preferred embodiment, the aerosol-cooling segment has an external diameter of 7.2 millimetres plus or minus 10 percent.

Preferably, the hollow tubular segment of the aerosol-cooling segment has an internal diameter of at least about 2 millimetres. More preferably, the hollow tubular segment of the aerosol-cooling segment has an internal diameter of at least about 2.5 millimetres. Even more preferably, the hollow tubular segment of the aerosol-cooling segment has an internal diameter of at least about 3 millimetres.

A peripheral wall of the aerosol-cooling segment may have a thickness of less than about 2.5 millimetres, preferably less than about 1.5 millimetres, more preferably less than about 1250 micrometres, even more preferably less than about 1000 micrometres. In particularly preferred embodiments, the peripheral wall of the aerosol-cooling segment has a thickness of less than about 900 micrometres, preferably less than about 800 micrometres.

In an embodiment, a peripheral wall of the aerosol-cooling segment has a thickness of about 2 millimetres.

The aerosol-cooling segment may have a length of between 5 millimetres and 25 millimetres.

Preferably, the aerosol-cooling segment has a length of at least about 8 millimetres, more preferably at least about 10 millimetres.

In preferred embodiments, the aerosol-cooling segment has a length of less than about 20 millimetres, more preferably less than about 15 millimetres.

In some embodiments, the aerosol-cooling segment has a length from about 5 millimetres to about 25 millimetres, preferably from about 8 millimetres to about 25 millimetres, more preferably from about 10 millimetres to about 25 millimetres. In other embodiments, the aerosol- cooling segment has a length from about 5 millimetres to about 20 millimetres, preferably from about 8 millimetres to about 20 millimetres, more preferably from about 10 millimetres to about 20 millimetres. In further embodiments, the aerosol-cooling segment has a length from about 5 millimetres to about 15 millimetres, preferably from about 8 millimetres to about 10 millimetres, more preferably from about 10 millimetres to about 15 millimetres.

In particularly preferred embodiments of the invention, the aerosol-cooling segment has a length of at least 10 millimetres. For example, in one particularly preferred embodiment, the aerosol-cooling segment has a length of 13 millimetres. In such embodiments, the aerosolcooling segment therefore has a relatively long length compared to the aerosol-cooling segments of prior art aerosol-generating articles.

A ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate may be from about 0.70 to about 1.50.

Preferably, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate is at least about 0.80, more preferably at least about 0.90, even more preferably at least about 1.00. In preferred embodiments, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate is less than about 1.40, more preferably less than about 1.30, even more preferably less than about 1.20.

In some embodiments, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate is from about 0.80 to about 1.40, preferably from about 0.90 to about 1 .40, more preferably from about 1.00 to about 1 .40. In other embodiments, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosolgenerating substrate is from about 0.80 to about 1.30, preferably from about 0.90 to about 1.30, more preferably from about 1.00 to about 1.30. In further embodiments, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate is from about 0.80 to about 1.20, preferably from about 0.90 to about 1.20, more preferably from about 1.00 to about 1.20.

In a particularly preferred embodiments, a ratio between the length of the aerosol-cooling segment and the length of the rod of aerosol-generating substrate is about 1 .08.

A ratio between the length of the aerosol-cooling segment and the length of the aerosolgenerating section may be from about 0.40 to about 1 .50.

Preferably, a ratio between the length of the aerosol-cooling segment and the length of the aerosol-generating section is at least about 0.50, more preferably at least about 0.60, even more preferably at least about 0.70. In preferred embodiments, a ratio between the length of the aerosol-cooling segment and the length of aerosol-generating section is less than about 1 .50, more preferably less than about 1.30, even more preferably less than about 1.10.

In some embodiments, a ratio between the length of the aerosol-cooling segment and the length of the aerosol-generating section is from about 0.50 to about 1 .50, preferably from about 0.60 to about 1 .50, more preferably from about 0.70 to about 1 .50. In other embodiments, a ratio between the length of the aerosol-cooling segment and the length of the aerosol-generating section is from about 0.50 to about 1.30, preferably from about 0.60 to about 1.30, more preferably from about 0.70 to about 1 .30. In further embodiments, a ratio between the length of the aerosolcooling segment and the length of the aerosol-generating section is from about 0.50 to about 1.10, preferably from about 0.60 to about 1.10, more preferably from about 0.70 to about 1.10.

In a particularly preferred embodiments, a ratio between the length of the aerosol-cooling segment and the length of the aerosol-generating section is about 0.77.

A ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article may be from about 0.225 to about 0.475.

Preferably, a ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is at least about 0.23, more preferably at least about 0.24, even more preferably at least about 0.25. A ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is preferably less than about 0.40, more preferably less than about 0.35, even more preferably less than about 0.30.

In some embodiments, a ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is preferably from about 0.23 to about 0.40, more preferably from about 0.24 to about 0.40, even more preferably from about 0.25 to about 0.40. In other embodiments, a ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is preferably from about 0.23 to about 0.35, more preferably from about 0.24 to about 0.35, even more preferably from about 0.25 to about 0.35. In further embodiments, a ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is preferably from about 0.23 to about 0.30, more preferably from about 0.24 to about 0.30, even more preferably from about 0.25 to about 0.30.

In a particularly preferred embodiment, a ratio between the length of the aerosol-cooling segment and the overall length of the aerosol-generating article is about 0.29.

Preferably, the length of the mouthpiece filter segment is at least 1 millimetre less than the length of the aerosol-cooling segment, more preferably at least 3 millimetres less than the length of the aerosol-cooling segment, more preferably at least 5 millimetres less than the length of the aerosol-cooling segment. A reduction in the length of the aerosol-cooling segment, as described above, can advantageously allow for an increase in the delivery of nicotine and glycerine to the consumer. The potential technical benefits of providing a relatively short mouthpiece filter segment are described above.

Preferably, the length of the mouthpiece section is at least 1 millimetre less than the length of the aerosol-cooling segment, more preferably at least 3 millimetres less than the length of the aerosol-cooling segment, more preferably at least 5 millimetres less than the length of the aerosolcooling segment. A reduction in the length of the aerosol-cooling segment, as described above, can advantageously allow for an increase in the delivery of nicotine and glycerine to the consumer. The potential technical benefits of providing a relatively short mouthpiece filter section are described above.

Preferably, in aerosol-generating articles in accordance with the present invention the aerosol-cooling segment has an average radial hardness of at least about 80 percent, more preferably at least about 85 percent, even more preferably at least about 90 percent. The aerosolcooling segment is therefore able to provide a desirable level of hardness to the aerosolgenerating article.

If desired, the radial hardness of the aerosol-cooling segment of aerosol-generating articles in accordance with the invention may be further increased by circumscribing the aerosolcooling segment by a stiff plug wrap, for example, a plug wrap having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm.

As used herein, the term “radial hardness” refers to resistance to compression in a direction transverse to a longitudinal axis of an segment. Radial hardness of an aerosolgenerating article around a given element may be determined by applying a load across the article at the location of the segment, transverse to the longitudinal axis of the article, and measuring the average (mean) depressed diameters of the articles. Radial hardness is given by: 100 % where Ds is the original (undepressed) diameter, and Dd is the depressed diameter after applying a set load for a set duration. The harder the material, the closer the hardness is to 100 percent.

To determine the hardness of a portion (such as a support segment or aerosol-cooling segment provided in the form of a hollow tube segment) of an aerosol article, aerosol-generating articles should be aligned parallel in a plane and the same portion of each aerosol-generating article to be tested should be subjected to a set load for a set duration. This test is performed using a known DD60A Densimeter device (manufactured and made commercially available by Heinr Borgwaldt GmbH, Germany), which is fitted with a measuring head for aerosol-generating articles, such as cigarettes, and with an aerosol-generating article receptacle.

The load is applied using two load-applying cylindrical rods, which extend across the diameter of all of the aerosol-generating articles at once. According to the standard test method for this instrument, the test should be performed such that twenty contact points occur between the aerosol-generating articles and the load applying cylindrical rods. In some cases, the hollow tube segments to be tested may be long enough such that only ten aerosol-generating articles are needed to form twenty contact points, with each smoking article contacting both load applying rods (because they are long enough to extend between the rods). In other cases, if the support segments are too short to achieve this, then twenty aerosol-generating articles should be used to form the twenty contact points, with each aerosol-generating article contacting only one of the load applying rods, as further discussed below.

Two further stationary cylindrical rods are located underneath the aerosol-generating articles, to support the aerosol-generating articles and counteract the load applied by each of the load applying cylindrical rods.

For the standard operating procedure for such an apparatus, an overall load of 2 kg is applied for a duration of 20 seconds. After 20 seconds have elapsed (and with the load still being applied to the smoking articles), the depression in the load applying cylindrical rods is determined, and then used to calculate the hardness from the above equation. The temperature is kept in the region of 22 degrees Celsius ± 2 degrees. The test described above is referred to as the DD60A Test. The standard way to measure the filter hardness is when the aerosol-generating article have not been consumed. Additional information regarding measurement of average radial hardness can be found in, for example, U.S. Published Patent Application Publication Number 2016/0128378.

The aerosol-cooling segment may be formed from any suitable material or combination of materials. For example, the aerosol-cooling segment may be formed from one or more materials selected from the group consisting of: cellulose acetate; cardboard; crimped paper, such as crimped heat resistant paper or crimped parchment paper; and polymeric materials, such as low density polyethylene (LDPE). Other suitable materials include polyhydroxyalkanoate (PHA) fibres.

In a preferred embodiment, the aerosol-cooling segment is formed from cellulose acetate.

Preferably, the hollow tubular segment of the aerosol-cooling segment is adapted to generate a RTD between approximately 0 millimetres H2O (about 0 Pa) to approximately 20 millimetres H2O (about 100 Pa), more preferably between approximately 0 millimetres H2O (about 0 Pa) to approximately 10 millimetres H2O (about 100 Pa).

In aerosol-generating articles in accordance with the present invention the overall RTD of the article depends essentially on the RTD of the rod of aerosol-generating substrate and optionally on the RTD of the mouthpiece and/or upstream plug. This is because the hollow tubular segment of the aerosol-cooling element and the hollow tubular segment of the support element are substantially empty and, as such, substantially only marginally contribute to the overall RTD of the aerosol-generating article.

The ventilation zone comprises a plurality of perforations through the peripheral wall of the aerosol-cooling segment. Preferably, the ventilation zone comprises at least one circumferential row of perforations. In some embodiments, the ventilation zone may comprise two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations.

An aerosol-generating article in accordance with the present invention may have a ventilation level of at least about 5 percent.

The term “ventilation level” is used throughout the present specification to denote a volume ratio between of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer.

The aerosol-generating article may typically have a ventilation level of at least about 10 percent, preferably at least about 15 percent, more preferably at least about 20 percent.

In preferred embodiments, the aerosol-generating article has a ventilation level of at least about 25 percent. The aerosol-generating article preferably has a ventilation level of less than about 60 percent. An aerosol-generating article in accordance with the present invention preferably has a ventilation level of less than or equal to about 45 percent. More preferably, an aerosol-generating article in accordance with the present invention has a ventilation level of less than or equal to about 40 percent , even more preferably less than or equal to about 35 percent.

In a particularly preferred embodiments, the aerosol-generating article has a ventilation level of about 30 percent. In some embodiments, the aerosol-generating article has a ventilation level from about 20 percent to about 60 percent, preferably from about 20 percent to about 45 percent, more preferably from about 20 percent to about 40 percent. In other embodiments, the aerosol-generating article has a ventilation level from about 25 percent to about 60 percent, preferably from about 25 percent to about 45 percent, more preferably from about 25 percent to about 40 percent. In further embodiments, the aerosol-generating article has a ventilation level from about 30 percent to about 60 percent, preferably from about 30 percent to about 45 percent, more preferably from about 30 percent to about 40 percent.

In particularly preferred embodiments, the aerosol-generating article has a ventilation level from about 28 percent to about 42 percent. In some particularly preferred embodiments, the aerosol-generating article has a ventilation level of about 30 percent.

Without wishing to be bound by theory, the inventors have found that the temperature drop caused by the admission of cooler, external air into the hollow tubular segment via the ventilation zone may have an advantageous effect on the nucleation and growth of aerosol particles.

Formation of an aerosol from a gaseous mixture containing various chemical species depends on a delicate interplay between nucleation, evaporation, and condensation, as well as coalescence, all the while accounting for variations in vapour concentration, temperature, and velocity fields. The so-called classical nucleation theory is based on the assumption that a fraction of the molecules in the gas phase are large enough to stay coherent for long times with sufficient probability (for example, a probability of one half). These molecules represent some kind of a critical, threshold molecule clusters among transient molecular aggregates, meaning that, on average, smaller molecule clusters are likely to disintegrate rather quickly into the gas phase, while larger clusters are, on average, likely to grow. Such critical cluster is identified as the key nucleation core from which droplets are expected to grow due to condensation of molecules from the vapour. It is assumed that virgin droplets that just nucleated emerge with a certain original diameter, and then may grow by several orders of magnitude. This is facilitated and may be enhanced by rapid cooling of the surrounding vapour, which induces condensation. In this connection, it helps to bear in mind that evaporation and condensation are two sides of one same mechanism, namely gas-liquid mass transfer. While evaporation relates to net mass transfer from the liquid droplets to the gas phase, condensation is net mass transfer from the gas phase to the droplet phase. Evaporation (or condensation) will make the droplets shrink (or grow), but it will not change the number of droplets.

In this scenario, which may be further complicated by coalescence phenomena, the temperature and rate of cooling can play a critical role in determining how the system responds. In general, different cooling rates may lead to significantly different temporal behaviours as concerns the formation of the liquid phase (droplets), because the nucleation process is typically nonlinear. Without wishing to be bound by theory, it is hypothesised that cooling can cause a rapid increase in the number concentration of droplets, which is followed by a strong, short-lived increase in this growth (nucleation burst). This nucleation burst would appear to be more significant at lower temperatures. Further, it would appear that higher cooling rates may favour an earlier onset of nucleation. By contrast, a reduction of the cooling rate would appear to have a favourable effect on the final size that the aerosol droplets ultimately reach.

Therefore, the rapid cooling induced by the admission of external air into the hollow tubular segment via the ventilation zone can be favourably used to favour nucleation and growth of aerosol droplets. However, at the same time, the admission of external air into the hollow tubular segment has the immediate drawback of diluting the aerosol stream delivered to the consumer.

The inventors have surprisingly found how the favourable effect of enhanced nucleation promoted by the rapid cooling induced by the introduction of ventilation air into the article is capable of significantly countering the less desirable effects of dilution. As such, satisfactory values of aerosol delivery are consistently achieved with aerosol-generating articles in accordance with the invention.

The inventors have also surprisingly found that the diluting effect on the aerosol - which can be assessed by measuring, in particular, the effect on the delivery of aerosol former (such as glycerol) included in the aerosol-generating substrate) is advantageously minimised when the ventilation level is within the ranges described above. In particular, ventilation levels between 25 percent and 50 percent, and even more preferably between 28 and 42 percent, have been found to lead to particularly satisfactory values of glycerine delivery. At the same time, the extent of nucleation and, as a consequence, the delivery of nicotine and aerosol-former (for example, glycerol) are enhanced.

This is particularly advantageous with “short” aerosol-generating articles, such as ones wherein a length of the rod of aerosol-generating substrate is less than about 40 millimetres, preferably less than 25 millimetres, even more preferably less than 20 millimetres, or wherein an overall length of the aerosol-generating article is less than about 70 millimetres, preferably less than about 60 millimetres, even more preferably less than 50 millimetres. As will be appreciated, in such aerosol-generating articles, there is little time and space for the aerosol to form and for the particulate phase of the aerosol to become available for delivery to the consumer.

Further, because the ventilated hollow tubular segment substantially does not contribute to the overall RTD of the aerosol-generating article, in aerosol-generating articles in accordance with the invention the overall RTD of the article can advantageously be fine-tuned by adjusting the length and density of the rod of aerosol-generating substrate or the length and optionally the length and density of a segment of filtration material forming part of the mouthpiece or the length and density of a segment of filtration material provided upstream of the aerosol-generating substrate and the susceptor element. Thus, aerosol-generating articles that have a predetermined RTD can be manufactured consistently and with great precision, such that satisfactory levels of RTD can be provided for the consumer even in the presence of ventilation.

In some embodiments, the intermediate hollow section may further comprise one or more additional aerosol-cooling segments which may be located downstream of the aerosol-cooling segment and abut the aerosol-cooling segment to form a continuous hollow section. In preferred embodiments, the additional aerosol-cooling segment comprises or is in the form of a hollow tubular segment. In a particularly preferred embodiment, the intermediate hollow section comprises a single additional aerosol-cooling segment, which may be located downstream of the aerosol-cooling segment and abut the aerosol-cooling segment.

In a preferred embodiment, the additional aerosol-cooling segment preferably has an external diameter that is approximately equal to the external diameter of the mouthpiece filter segment and the external diameter of the aerosol-generating article. The additional aerosolcooling segment may have an external diameter of between about 5 millimetres and about 10 millimetres, or between about 6 millimetres and about 8 millimetres. In a preferred embodiment, the additional aerosol-cooling segment has an external diameter of approximately 7.2 millimetres.

Preferably, the hollow tubular segment of the additional aerosol-cooling segment has an internal diameter of at least about 2 millimetres. More preferably, the hollow tubular segment of the additional aerosol-cooling segment has an internal diameter of at least about 2.5 millimetres. Even more preferably, the hollow tubular segment of the additional aerosol-cooling segment has an internal diameter of at least about 3 millimetres. A peripheral wall of the additional aerosol-cooling segment may have a thickness of less than about 2.5 millimetres, preferably less than about 1.5 millimetres, more preferably less than about 1250 micrometres, even more preferably less than about 1000 micrometres. In particularly preferred embodiments, the peripheral wall of the additional aerosol-cooling segment has a thickness of less than about 900 micrometres, preferably less than about 800 micrometres.

In an embodiment, a peripheral wall of the additional aerosol-cooling segment has a thickness of about 2 millimetres.

The additional aerosol-cooling segment may have a length of from about 5 millimetres to less than about 10 millimetres.

In a particularly preferred embodiment, the aerosol-cooling segment has a length of 8 millimetres and the additional aerosol-cooling segment has a length of 5 millimetres.

As described above, the intermediate hollow section of aerosol-generating articles according to the invention further comprises a support segment arranged in alignment with, and downstream of the aerosol-generating section. In particular, the support segment may be located immediately downstream of the rod of aerosol-generating substrate and may abut the rod of aerosol-generating substrate.

The support segment may be formed from any suitable material or combination of materials. For example, the support segment may be formed from one or more materials selected from the group consisting of: cellulose acetate; cardboard; crimped paper, such as crimped heat resistant paper or crimped parchment paper; and polymeric materials, such as low density polyethylene (LDPE). In a preferred embodiment, the support segment is formed from cellulose acetate. Other suitable materials include polyhydroxyalkanoate (PHA) fibres.

The support segment may comprise a hollow tubular segment. In a preferred embodiment, the support element comprises a hollow cellulose acetate tube.

The support segment is arranged substantially in alignment with the rod. This means that the length dimension of the support segment is arranged to be approximately parallel to the longitudinal direction of the rod and of the article, for example within plus or minus 10 degrees of parallel to the longitudinal direction of the rod. In preferred embodiments, the support segment extends along the longitudinal axis of the rod.

The support segment preferably has an outer diameter that is approximately equal to the outer diameter of the rod of aerosol-generating substrate and to the outer diameter of the aerosolgenerating article.

The support segment may have an outer diameter of between 5 millimetres and 12 millimetres, for example of between 5 millimetres and 10 millimetres or of between 6 millimetres and 8 millimetres. In a preferred embodiment, the support segment has an external diameter of 7.2 millimetres plus or minus 10 percent. A peripheral wall of the support segment may have a thickness of at least 1 millimetre, preferably at least about 1 .5 millimetres, more preferably at least about 2 millimetres.

The support segment may have a length of between about 5 millimetres and about 15 millimetres.

Preferably, the support segment has a length of at least about 6 millimetres, more preferably at least about 7 millimetres.

In preferred embodiments, the support segment has a length of less than about 12 millimetres, more preferably less than about 10 millimetres.

In some embodiments, the support segment has a length from about 5 millimetres to about 15 millimetres, preferably from about 6 millimetres to about 15 millimetres, more preferably from about 7 millimetres to about 15 millimetres. In other embodiments, the support segment has a length from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 12 millimetres, more preferably from about 7 millimetres to about 12 millimetres. In further embodiments, the support segment has a length from about 5 millimetres to about 10 millimetres, preferably from about 6 millimetres to about 10 millimetres, more preferably from about 7 millimetres to about 10 millimetres.

In a preferred embodiment, the support segment has a length of about 8 millimetres.

Preferably, the total length of the intermediate hollow section is no more than about 23 millimetres, more preferably no more than about 22 millimetres, most preferably no more than about 21 millimetres. Preferably, the total length of the intermediate hollow section is more than about 16 millimetres, more preferably more than about 18 millimetres. The total length of the intermediate hollow section may be more than about 16 millimetres and no more than about 23 millimetres, preferably more than about 16 millimetres and no more than about 22 millimetres, most preferably more than about 16 millimetres and no more than about 21 millimetres. The total length of the intermediate hollow section may be more than about 18 millimetres and no more than about 23 millimetres, more preferably more than about 18 millimetres and no more than about 22 millimetres, most preferably more than about 18 millimetres and no more than about 21 millimetres.

In a preferred embodiment, the intermediate hollow section has a length of about 21 millimetres.

A ratio between the length of the support segment and the length of the rod of aerosolgenerating substrate may be from about 0.25 to about 1.00.

Preferably, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is at least about 0.30, more preferably at least about 0.40, even more preferably at least about 0.50. In preferred embodiments, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is less than about 0.90, more preferably less than about 0.80, even more preferably less than about 0.70. In some embodiments, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is from about 0.30 to about 0.90, preferably from about 0.40 to about 0.90, more preferably from about 0.50 to about 0.90. In other embodiments, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is from about 0.30 to about 0.80, preferably from about 0.40 to about 0.80, more preferably from about 0.50 to about 0.80. In further embodiments, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is from about 0.30 to about 0.70, preferably from about 0.40 to about 0.70, more preferably from about 0.50 to about 0.70.

In a particularly preferred embodiment, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is about 0.66.

A ratio between the length of the support segment and the length of the aerosol-generating section may be from about 0.25 to about 1.00.

Preferably, a ratio between the length of the support segment and the length of aerosolgenerating section is at least about 0.30, more preferably at least about 0.40, even more preferably at least about 0.45. In preferred embodiments, a ratio between the length of the support segment and the length of the rod of aerosol-generating substrate is less than about 0.90, more preferably less than about 0.80, even more preferably less than about 0.70.

In some embodiments, a ratio between the length of the support segment and the length of the aerosol-generating section is from about 0.30 to about 0.90, preferably from about 0.40 to about 0.90, more preferably from about 0.45 to about 0.90. In other embodiments, a ratio between the length of the support segment and the length of the aerosol-generating section is from about 0.30 to about 0.80, preferably from about 0.40 to about 0.80, more preferably from about 0.45 to about 0.80. In further embodiments, a ratio between the length of the support segment and the length of the aerosol-generating section is from about 0.30 to about 0.70, preferably from about 0.40 to about 0.70, more preferably from about 0.45 to about 0.70.

In a particularly preferred embodiment, a ratio between the length of the support segment and the length of the aerosol-generating section is about 0.47.

A ratio between the length of the support segment and the overall length of the aerosolgenerating article may be from about 0.125 to about 0.375.

Preferably, a ratio between the length of the support segment and the overall length of the aerosol-generating article is at least about 0.13, more preferably at least about 0.14, even more preferably at least about 0.15. A ratio between the length of the support segment and the overall length of the aerosol-generating article is preferably less than about 0.30, more preferably less than about 0.25, even more preferably less than about 0.20.

In some embodiments, a ratio between the length of the support segment and the overall length of the aerosol-generating article is preferably from about 0.13 to about 0.30, more preferably from about 0.14 to about 0.30, even more preferably from about 0.15 to about 0.30. In other embodiments, a ratio between the length of the support segment and the overall length of the aerosol-generating article is preferably from about 0.13 to about 0.25, more preferably from about 0.14 to about 0.25, even more preferably from about 0.15 to about 0.25. In further embodiments, a ratio between the length of the support segment and the overall length of the aerosol-generating article is preferably from about 0.13 to about 0.20, more preferably from about 0.14 to about 0.20, even more preferably from about 0.15 to about 0.20.

In a particularly preferred embodiment, a ratio between the length of the support segment and the overall length of the aerosol-generating article is about 0.18.

Preferably, in aerosol-generating articles in accordance with the present invention the support segment has an average radial hardness of at least about 80 percent, more preferably at least about 85 percent, even more preferably at least about 90 percent. The support segment is therefore able to provide a desirable level of hardness to the aerosol-generating article.

If desired, the radial hardness of the support segment of aerosol-generating articles in accordance with the invention may be further increased by circumscribing the support element by a stiff plug wrap, for example, a plug wrap having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm.

During insertion of an aerosol-generating article in accordance with the invention into an aerosol-generating device for heating the aerosol-generating substrate, a user may be required to apply some force in order to overcome the resistance of the aerosol-generating substrate of the aerosol-generating article to insertion. This may damage one or both of the aerosolgenerating article and the aerosol-generating device. In addition, the application of force during insertion of the aerosol-generating article into the aerosol-generating device may displace the aerosol-generating substrate within the aerosol-generating article. This may result in the heating element of the aerosol-generating device not being properly aligned with the susceptor element provided within the aerosol-generating substrate, which may lead to uneven and inefficient heating of the aerosol-generating substrate of the aerosol-generating article. The support segment is advantageously configured to resist downstream movement of the aerosol-generating substrate during insertion of the article into the aerosol-generating device.

Preferably, the hollow tubular segment of the support segment is adapted to generate a RTD between approximately 0 millimetres H2O (about 0 Pa) to approximately 20 millimetres H2O (about 100 Pa), more preferably between approximately 0 millimetres H2O (about 0 Pa) to approximately 10 millimetres H2O (about 100 Pa). The support segment therefore preferably does not contribute to the overall RTD of the aerosol-generating article.

In some embodiments wherein the intermediate hollow section comprises both a support segment comprising a first hollow tube segment and an aerosol-cooling segment comprising a second hollow tubular segment, the internal diameter (DSTS) of the second hollow tubular segment is preferably greater than the internal diameter (DFTS) of the first hollow tubular segment.

In more detail, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably at least about 1.25. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably at least about 1.30. Even more preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably at least about 1.40. In particularly preferred embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is at least about 1.50, more preferably at least about 1.60.

A ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably less than or equal to about 2.50. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably less than or equal to about 2.25. Even more preferably, ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is preferably less than or equal to about 2.00.

In some embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.25 to about 2.50. Preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.30 to about 2.50. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.40 to about 2.50. In particularly preferred embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.50 to about 2.50.

In other embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.25 to about 2.25. Preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.30 to about 2.25. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.40 to about 2.25. In particularly preferred embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.50 to about 2.25. In further embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1 .25 to about 2.00. Preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1 .30 to about 2.00. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.40 to about 2.00. In particularly preferred embodiments, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and the internal diameter (DFTS) of the first hollow tubular segment is from about 1.50 to about 2.00.

In those embodiments wherein the article further comprises an elongate susceptor element arranged longitudinally within the aerosol-generating substrate, as described below, a ratio between the internal diameter (DFTS) of the first hollow tubular segment and a width of the susceptor element is preferably at least about 0.20. More preferably, a ratio between the internal diameter (DFTS) of the first hollow tubular segment and a width of the susceptor element is at least about 0.30. Even more preferably, a ratio between the internal diameter (DFTS) of the first hollow tubular segment and a width of the susceptor element is at least about 0.40.

In addition, or as an alternative, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and a width of the susceptor element is preferably at least about 0.20. More preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and a width of the susceptor element is at least about 0.50. Even more preferably, a ratio between the internal diameter (DSTS) of the second hollow tubular segment and a width of the susceptor element is at least about 0.80.

Preferably, a ratio between a volume of the cavity of the first hollow tubular segment and a volume of the cavity of the second hollow tubular segment is at least about 0.10. More preferably, a ratio between a volume of the cavity of the first hollow tubular segment and a volume of the cavity of second hollow tubular segment is at least about 0.20.

A ratio between a volume of the cavity of the first hollow tubular segment and a volume of the cavity of the second hollow tubular segment is preferably less than or equal to about 0.40. More preferably, a ratio between a volume of the cavity of the first hollow tubular segment and a volume of the cavity of the second hollow tubular segment is preferably less than or equal to about 0.30.

As defined above, the aerosol-generating article of the present invention comprises an aerosol-generating section comprising a rod of an aerosol-generating substrate.

The aerosol-generating substrate may be any suitable solid aerosol-generating substrate, such as an aerosol-generating substrate comprising a homogenised plant material; a gel composition that includes an alkaloid compound, or a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound; a solid aerosol-generating film; or an aerosol- generating substrate comprising thermally conductive particles. Preferably, the aerosolgenerating substrate is a solid aerosol-generating film.

In certain preferred embodiments, the aerosol-generating substrate comprises homogenised plant material, preferably a homogenised tobacco material.

As used herein, the term “homogenised plant material” encompasses any plant material formed by the agglomeration of particles of plant. For example, sheets or webs of homogenised tobacco material for the aerosol-generating substrates of the present invention may be formed by agglomerating particles of tobacco material obtained by pulverising, grinding or comminuting plant material and optionally one or more of tobacco leaf lamina and tobacco leaf stems. The homogenised plant material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

The homogenised plant material can be provided in any suitable form. For example, the homogenised plant material may be in the form of one or more sheets. As used herein, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof.

Alternatively or in addition, the homogenised plant material may be in the form of a plurality of pellets or granules.

Alternatively or in addition, the homogenised plant material may be in the form of a plurality of strands, strips or shreds. As used herein, the term “strand” describes an elongate element of material having a length that is substantially greater than the width and thickness thereof. The term “strand” should be considered to encompass strips, shreds and any other homogenised plant material having a similar form. The strands of homogenised plant material may be formed from a sheet of homogenised plant material, for example by cutting or shredding, or by other methods, for example, by an extrusion method.

In some embodiments, the strands may be formed in situ within the aerosol-generating substrate as a result of the splitting or cracking of a sheet of homogenised plant material during formation of the aerosol-generating substrate, for example, as a result of crimping. The strands of homogenised plant material within the aerosol-generating substrate may be separate from each other. Alternatively, each strand of homogenised plant material within the aerosolgenerating substrate may be at least partially connected to an adjacent strand or strands along the length of the strands. For example, adjacent strands may be connected by one or more fibres. This may occur, for example, where the strands have been formed due to the splitting of a sheet of homogenised plant material during production of the aerosol-generating substrate, as described above.

Preferably, the aerosol-generating substrate is in the form of one or more sheets of homogenised plant material. In various embodiments of the invention, the one or more sheets of homogenised plant material may be produced by a casting process. In various embodiments of the invention, the one or more sheets of homogenised plant material may be produced by a papermaking process. The one or more sheets as described herein may each individually have a thickness of between 100 micrometres and 600 micrometres, preferably between 150 micrometres and 300 micrometres, and most preferably between 200 micrometres and 250 micrometres. Individual thickness refers to the thickness of the individual sheet, whereas combined thickness refers to the total thickness of all sheets that make up the aerosol-generating substrate. For example, if the aerosol-generating substrate is formed from two individual sheets, then the combined thickness is the sum of the thickness of the two individual sheets or the measured thickness of the two sheets where the two sheets are stacked in the aerosol-generating substrate.

The one or more sheets as described herein may each individually have a grammage of between about 100 g/m² and about 300 g/m².

The one or more sheets as described herein may each individually have a density of from about 0.3 g/cm³to about 1.3 g/cm³, and preferably from about 0.7 g/cm³ to about 1.0 g/cm³.

In embodiments of the present invention in which the aerosol-generating substrate comprises one or more sheets of homogenised plant material, the sheets are preferably in the form of one or more gathered sheets. As used herein, the term “gathered sheet” may refer to a sheet of an aerosol-generating substrate or aerosol-generating article that is convoluted, folded, or otherwise compressed or constricted substantially transversely to a longitudinal axis of the aerosol-generating substrate, or aerosol-generating article, or otherwise compressed or constricted substantially transversely to the cylindrical axis of a plug or a rod.

The one or more sheets of homogenised plant material may be gathered transversely relative to the longitudinal axis thereof and circumscribed with a wrapper to form a continuous rod or a plug.

The one or more sheets of homogenised plant material may advantageously be crimped or similarly treated. As used herein, the term “crimped” denotes a sheet having a plurality of substantially parallel ridges or corrugations. Alternatively or in addition to being crimped, the one or more sheets of homogenised plant material may be embossed, debossed, perforated or otherwise deformed to provide texture on one or both sides of the sheet.

Preferably, each sheet of homogenised plant material may be crimped such that it has a plurality of ridges or corrugations substantially parallel to the cylindrical axis of the plug. This treatment advantageously facilitates gathering of the crimped sheet of homogenised plant material to form the plug. Preferably, the one or more sheets of homogenised plant material may be gathered. It will be appreciated that crimped sheets of homogenised plant material may alternatively or in addition have a plurality of substantially parallel ridges or corrugations disposed at an acute or obtuse angle to the cylindrical axis of the plug. The sheet may be crimped to such an extent that the integrity of the sheet becomes disrupted at the plurality of parallel ridges or corrugations causing separation of the material, and results in the formation of shreds, strands or strips of homogenised plant material.

Alternatively, the one or more sheets of homogenised plant material may be cut into strands as referred to above. In such embodiments, the aerosol-generating substrate comprises a plurality of strands of the homogenised plant material. The strands may be used to form a plug. Typically, the width of such strands is about 5 millimetres, or about 4 millimetres, or about 3 millimetres, or about 2 millimetres or less. The length of the strands may be greater than about 5 millimetres, between about 5 millimetres to about 15 millimetres, about 8 millimetres to about 12 millimetres, or about 12 millimetres. Preferably, the strands have substantially the same length as each other. The length of the strands may be determined by the manufacturing process whereby a rod is cut into shorter plugs and the length of the strands corresponds to the length of the plug. The strands may be fragile which may result in breakage especially during transit. In such cases, the length of some of the strands may be less than the length of the plug.

The plurality of strands preferably extend substantially longitudinally along the length of the aerosol-generating substrate, aligned with the longitudinal axis. Preferably, the plurality of strands are therefore aligned substantially parallel to each other.

The homogenised plant material may comprise up to about 95 percent by weight of plant particles, on a dry weight basis. Preferably, the homogenised plant material comprises up to about 90 percent by weight of plant particles, more preferably up to about 80 percent by weight of plant particles, more preferably up to about 70 percent by weight of plant particles, more preferably up to about 60 percent by weight of plant particles, more preferably up to about 50 percent by weight of plant particles, on a dry weight basis.

For example, the homogenised plant material may comprise between about 2.5 percent and about 95 percent by weight of plant particles, or about 5 percent and about 90 percent by weight of plant particles, or between about 10 percent and about 80 percent by weight of plant particles, or between about 15 percent and about 70 percent by weight of plant particles, or between about 20 percent and about 60 percent by weight of plant particles, or between about 30 percent and about 50 percent by weight of plant particles, on a dry weight basis.

In certain embodiments of the invention, the homogenised plant material is a homogenised tobacco material comprising tobacco particles. Sheets of homogenised tobacco material for use in such embodiments of the invention may have a tobacco content of at least about 40 percent by weight on a dry weight basis, more preferably of at least about 50 percent by weight on a dry weight basis, more preferably at least about 70 percent by weight on a dry weight basis and most preferably at least about 90 percent by weight on a dry weight basis.

The term “tobacco particles” describes particles of any plant member of the genus Nicotiana. The term “tobacco particles” encompasses ground or powdered tobacco leaf lamina, ground or powdered tobacco leaf stems, tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco. In a preferred embodiment, the tobacco particles are substantially all derived from tobacco leaf lamina. By contrast, isolated nicotine and nicotine salts are compounds derived from tobacco but are not considered tobacco particles for purposes of the invention and are not included in the percentage of particulate plant material.

The tobacco particles may be prepared from one or more varieties of tobacco plants. Any type of tobacco may be used in a blend. Examples of tobacco types that may be used include, but are not limited to, sun-cured tobacco, flue-cured tobacco, Burley tobacco, Maryland tobacco, Oriental tobacco, Virginia tobacco, and other speciality tobaccos.

Flue-curing is a method of curing tobacco, which is particularly used with Virginia tobaccos. During the flue-curing process, heated air is circulated through densely packed tobacco. During a first stage, the tobacco leaves turn yellow and wilt. During a second stage, the laminae of the leaves are completely dried. During a third stage, the leaf stems are completely dried.

Burley tobacco plays a significant role in many tobacco blends. Burley tobacco has a distinctive flavour and aroma and also has an ability to absorb large amounts of casing.

Oriental is a type of tobacco which has small leaves, and high aromatic qualities. However, Oriental tobacco has a milder flavour than, for example, Burley. Generally, therefore, Oriental tobacco is used in relatively small proportions in tobacco blends.

Kasturi, Madura and Jatim are subtypes of sun-cured tobacco that can be used. Preferably, Kasturi tobacco and flue-cured tobacco may be used in a blend to produce the tobacco particles. Accordingly, the tobacco particles in the particulate plant material may comprise a blend of Kasturi tobacco and flue-cured tobacco.

The tobacco particles may have a nicotine content of at least about 2.5 percent by weight, based on dry weight. More preferably, the tobacco particles may have a nicotine content of at least about 3 percent, even more preferably at least about 3.2 percent, even more preferably at least about 3.5 percent, most preferably at least about 4 percent by weight, based on dry weight.

In certain other embodiments of the invention, the homogenised plant material comprises tobacco particles in combination with non-tobacco plant flavour particles. Preferably, the nontobacco plant flavour particles are selected from one or more of: ginger particles, rosemary particles, eucalyptus particles, clove particles and star anise particles. Preferably, in such embodiments, the homogenised plant material comprises at least about 2.5 percent by weight of the non-tobacco plant flavour particles, on a dry weight basis, with the remainder of the plant particles being tobacco particles. Preferably, the homogenised plant material comprises at least about 4 percent by weight of non-tobacco plant flavour particles, more preferably at least about 6 percent by weight of non-tobacco plant flavour particles, more preferably at least about 8 percent by weight of non-tobacco plant flavour particles and more preferably at least about 10 percent by weight of non-tobacco plant flavour particles, on a dry weight basis. Preferably, the homogenised plant material comprises up to about 20 percent by weight of non-tobacco plant flavour particles, more preferably up to about 18 percent by weight of non-tobacco plant flavour particles, more preferably up to about 16 percent by weight of non-tobacco plant flavour particles.

The weight ratio of the non-tobacco plant flavour particles and the tobacco particles in the particulate plant material forming the homogenised plant material may vary depending on the desired flavour characteristics and composition of the aerosol produced from the aerosolgenerating substrate during use. Preferably, the homogenised plant material comprises at least a 1 :30 weight ratio of non-tobacco plant flavour particles to tobacco particles, more preferably at least a 1 :20 weight ratio of non-tobacco plant flavour particles to tobacco particles, more preferably at least a 1 :10 weight ratio of non-tobacco plant flavour particles to tobacco particles and most preferably at least a 1 :5 weight ratio of non-tobacco plant flavour particles to tobacco particles, on a dry weight basis.

Alternatively or in addition to the inclusion of tobacco particles into the homogenised plant material of the aerosol-generating substrate according to the invention, the homogenised plant material may comprise cannabis particles. The term “cannabis particles” refers to particles of a cannabis plant, such as the species Cannabis sativa, Cannabis indica, and Cannabis ruderalis.

The homogenised plant material preferably comprises no more than 95 percent by weight of the particulate plant material, on a dry weight basis. The particulate plant material is therefore typically combined with one or more other components to form the homogenised plant material.

The homogenised plant material may further comprise a binder to alter the mechanical properties of the particulate plant material, wherein the binder is included in the homogenised plant material during manufacturing as described herein. Suitable exogenous binders would be known to the skilled person and include but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins; and combinations thereof. Preferably, the binder comprises guar gum.

The binder may be present in an amount of from about 1 percent to about 10 percent by weight, based on the dry weight of the homogenised plant material, preferably in an amount of from about 2 percent to about 5 percent by weight, based on the dry weight of the homogenised plant material.

Alternatively or in addition, the homogenised plant material may further comprise one or more lipids to facilitate the diffusivity of volatile components (for example, aerosol formers, gingerols and nicotine), wherein the lipid is included in the homogenised plant material during manufacturing as described herein. Suitable lipids for inclusion in the homogenised plant material include, but are not limited to: medium-chain triglycerides, cocoa butter, palm oil, palm kernel oil, mango oil, shea butter, soybean oil, cottonseed oil, coconut oil, hydrogenated coconut oil, candellila wax, carnauba wax, shellac, sunflower wax, sunflower oil, rice bran, and Revel A; and combinations thereof.

Alternatively or in addition, the homogenised plant material may further comprise a pH modifier.

Alternatively or in addition, the homogenised plant material may further comprise fibres to alter the mechanical properties of the homogenised plant material, wherein the fibres are included in the homogenised plant material during manufacturing as described herein. Suitable exogenous fibres for inclusion in the homogenised plant material are known in the art and include fibres formed from non-tobacco material and non- ginger material, including but not limited to: cellulose fibres; soft-wood fibres; hard-wood fibres; jute fibres and combinations thereof. Exogenous fibres derived from tobacco and/or ginger can also be added. Any fibres added to the homogenised plant material are not considered to form part of the “particulate plant material” as defined above. Prior to inclusion in the homogenised plant material, fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping; refining; chemical pulping; bleaching; sulfate pulping; and combinations thereof. A fibre typically has a length greater than its width.

Suitable fibres typically have lengths of greater than 400 micrometres and less than or equal to 4 millimetres, preferably within the range of 0.7 millimetres to 4 millimetres. Preferably, the fibres are present in an amount of about 2 percent to about 15 percent by weight, most preferably at about 4 percent by weight, based on the dry weight of the substrate.

Alternatively or in addition, the homogenised plant material may further comprise one or more aerosol formers. Upon volatilisation, an aerosol former can convey other vaporised compounds released from the aerosol-generating substrate upon heating, such as nicotine and flavourants, in an aerosol. Suitable aerosol formers for inclusion in the homogenised plant material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1 ,3-butanediol and glycerol; 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.

The homogenised plant material may have an aerosol former content of between about 5 percent and about 30 percent by weight on a dry weight basis, such as between about 10 percent and about 25 percent by weight on a dry weight basis, or between about 15 percent and about 20 percent by weight on a dry weight basis.

For example, if the substrate is intended for use in an aerosol-generating article for an electrically-operated aerosol-generating system having a heating element, it may preferably include an aerosol former content of between about 5 percent to about 30 percent by weight on a dry weight basis. If the substrate is intended for use in an aerosol-generating article for an electrically-operated aerosol-generating system having a heating element, the aerosol former is preferably glycerol.

In other embodiments, the homogenised plant material may have an aerosol former content of about 1 percent to about 5 percent by weight on a dry weight basis. For example, if the substrate is intended for use in an aerosol-generating article in which aerosol former is kept in a reservoir separate from the substrate, the substrate may have an aerosol former content of greater than 1 percent and less than about 5 percent. In such embodiments, the aerosol former is volatilised upon heating and a stream of the aerosol former is contacted with the aerosolgenerating substrate so as to entrain the flavours from the aerosol-generating substrate in the aerosol.

In other embodiments, the homogenised plant material may have an aerosol former content of about 30 percent by weight to about 45 percent by weight. This relatively high level of aerosol former is particularly suitable for aerosol-generating substrates that are intended to be heated at a temperature of less than 275 degrees Celsius. In such embodiments, the homogenised plant material preferably further comprises between about 2 percent by weight and about 10 percent by weight of cellulose ether, on a dry weight basis and between about 5 percent by weight and about 50 percent by weight of additional cellulose, on a dry weight basis. The use of the combination of cellulose ether and additional cellulose has been found to provide a particularly effective delivery of aerosol when used in an aerosol-generating substrate having an aerosol former content of between 30 percent by weight and 45 percent by weight.

Suitable cellulose ethers include but are not limited to methyl cellulose, hydroxypropyl methyl cellulose, ethyl cellulose, hydroxyl ethyl cellulose, hydroxyl propyl cellulose, ethyl hydroxyl ethyl cellulose and carboxymethyl cellulose (CMC). In particularly preferred embodiments, the cellulose ether is carboxymethyl cellulose.

As used herein, the term “additional cellulose” encompasses any cellulosic material incorporated into the homogenised plant material which does not derive from the non-tobacco plant particles or tobacco particles provided in the homogenised plant material. The additional cellulose is therefore incorporated in the homogenised plant material in addition to the nontobacco plant material or tobacco material, as a separate and distinct source of cellulose to any cellulose intrinsically provided within the non-tobacco plant particles or tobacco particles. The additional cellulose will typically derive from a different plant to the non-tobacco plant particles or tobacco particles. Preferably, the additional cellulose is in the form of an inert cellulosic material, which is sensorially inert and therefore does not substantially impact the organoleptic characteristics of the aerosol generated from the aerosol-generating substrate. For example, the additional cellulose is preferably a tasteless and odourless material. The additional cellulose may comprise cellulose powder, cellulose fibres, or a combination thereof.

The aerosol former may act as a humectant in the aerosol-generating substrate.

The wrapper circumscribing the rod of homogenised plant material may be a paper wrapper or a non-paper wrapper. Suitable paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps. Suitable non-paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to sheets of homogenised tobacco materials. In certain preferred embodiments, the wrapper may be formed of a laminate material comprising a plurality of layers. Preferably, the wrapper is formed of an aluminium co-laminated sheet. The use of a co-laminated sheet comprising aluminium advantageously prevents combustion of the aerosolgenerating substrate in the event that the aerosol-generating substrate should be ignited, rather than heated in the intended manner.

In other preferred embodiments of the present invention, the aerosol-generating substrate comprises a gel composition that includes an alkaloid compound, or a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound. In particularly preferred embodiments, the aerosol-generating substrate comprises a gel composition that includes nicotine.

Preferably, the gel composition comprises an alkaloid compound, or a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound; an aerosol former; and at least one gelling agent. Preferably, the at least one gelling agent forms a solid medium and the glycerol is dispersed in the solid medium, with the alkaloid or cannabinoid dispersed in the glycerol. Preferably, the gel composition is a stable gel phase.

Advantageously, a stable gel composition comprising nicotine provides predictable composition form upon storage or transit from manufacture to the consumer. The stable gel composition comprising nicotine substantially maintains its shape. The stable gel composition comprising nicotine substantially does not release a liquid phase upon storage or transit from manufacture to the consumer. The stable gel composition comprising nicotine may provide for a simple consumable design. This consumable may not have to be designed to contain a liquid, thus a wider range of materials and container constructions may be contemplated.

The gel composition described herein may be combined with an aerosol-generating device to provide a nicotine aerosol to the lungs at inhalation or air flow rates that are within conventional smoking regime inhalation or air flow rates. The aerosol-generating device may continuously heat the gel composition. A consumer may take a plurality of inhalations or “puffs” where each “puff” delivers an amount of nicotine aerosol. The gel composition may be capable of delivering a high nicotine/low total particulate matter (TPM) aerosol to a consumer when heated, preferably in a continuous manner. The phrase “stable gel phase” or “stable gel” refers to gel that substantially maintains its shape and mass when exposed to a variety of environmental conditions. The stable gel may not substantially release (sweat) or absorb water when exposed to a standard temperature and pressure while varying relative humidity from about 10 percent to about 60 percent. For example, the stable gel may substantially maintain its shape and mass when exposed to a standard temperature and pressure while varying relative humidity from about 10 percent to about 60 percent.

The gel composition includes an alkaloid compound, or a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound. The gel composition may include one or more alkaloids. The gel composition may include one or more cannabinoids. The gel composition may include a combination of one or more alkaloids and one or more cannabinoids.

The term “alkaloid compound” refers to any one of a class of naturally occurring organic compounds that contain one or more basic nitrogen atoms. Generally, an alkaloid contains at least one nitrogen atom in an amine-type structure. This or another nitrogen atom in the molecule of the alkaloid compound can be active as a base in acid-base reactions. Most alkaloid compounds have one or more of their nitrogen atoms as part of a cyclic system, such as for example a heterocylic ring. In nature, alkaloid compounds are found primarily in plants, and are especially common in certain families of flowering plants. However, some alkaloid compounds are found in animal species and fungi. In this disclosure, the term “alkaloid compound” refers to both naturally derived alkaloid compounds and synthetically manufactured alkaloid compounds.

The gel composition may preferably include an alkaloid compound selected from the group consisting of nicotine, anatabine, and combinations thereof.

Preferably the gel composition includes nicotine.

The term “nicotine” refers to nicotine and nicotine derivatives such as free-base nicotine, nicotine salts and the like.

The term “cannabinoid compound” refers to any one of a class of naturally occurring compounds that are found in parts of the cannabis plant - namely the species Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Cannabinoid compounds are especially concentrated in the female flower heads. Cannabinoid compounds naturally occurring in the cannabis plant include cannabidiol (CBD) and tetrahydrocannabinol (THC). In this disclosure, the term “cannabinoid compounds” is used to describe both naturally derived cannabinoid compounds and synthetically manufactured cannabinoid compounds.

The gel may include a cannabinoid compound selected from the group consisting of cannabidiol (CBD), tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabichromene (CBC), cannabicyclol (CBL), cannabivarin (CBV), tetrahydrocannabivarin (THCV), cannabidivarin (CBDV), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabigerol monomethyl ether (CBGM), cannabielsoin (CBE),cannabicitran (CBT), and combinations thereof.

The gel composition may preferably include a cannabinoid compound selected from the group consisting of cannabidiol (CBD), THC (tetrahydrocannabinol) and combinations thereof.

The gel may preferably include cannabidiol (CBD).

The gel composition may include nicotine and cannabidiol (CBD).

The gel composition may include nicotine, cannabidiol (CBD), and THC (tetrahydrocannabinol).

The gel composition preferably includes about 0.5 percent by weight to about 10 percent by weight of an alkaloid compound, or about 0.5 percent by weight to about 10 percent by weight, of a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound in a total amount from about 0.5 percent by weight to about 10 percent by weight. The gel composition may include about 0.5 percent by weight to about 5 percent by weight of an alkaloid compound, or about 0.5 percent by weight to about 5 percent by weight of a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound in a total amount from about 0.5 percent by weight to about 5 percent by weight. Preferably the gel composition includes about 1 percent by weight to about 3 percent by weight of an alkaloid compound, or about 1 percent by weight to about 3 percent by weight of a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound in a total amount from about 1 percent by weight to about 3 percent by weight. The gel composition may preferably include about 1.5 percent by weight to about 2.5 percent by weight of an alkaloid compound, or about 1 .5 percent by weight to about 2.5 percent by weight of a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound in a total amount from about 1.5 percent by weight to about 2.5 percent by weight. The gel composition may preferably include about 2 percent by weight of an alkaloid compound, or about 2 percent by weight of a cannabinoid compound, or both an alkaloid compound and a cannabinoid compound in a total amount of about 2 percent by weight. The alkaloid compound component of the gel formulation may be the most volatile component of the gel formulation. In some aspects water may be the most volatile component of the gel formulation and the alkaloid compound component of the gel formulation may be the second most volatile component of the gel formulation. The cannabinoid compound component of the gel formulation may be the most volatile component of the gel formulation. In some aspects water may be the most volatile component of the gel formulation and the alkaloid compound component of the gel formulation may be the second most volatile component of the gel formulation.

Preferably nicotine is included in the gel compositions. The nicotine may be added to the composition in a free base form or a salt form. The gel composition includes about 0.5 percent by weight to about 10 percent by weight nicotine, or about 0.5 percent by weight to about 5 percent by weight nicotine. Preferably the gel composition includes about 1 percent by weight to about 3 percent by weight nicotine, or about 1 .5 percent by weight to about 2.5 percent by weight nicotine, or about 2 percent by weight nicotine. The nicotine component of the gel formulation may be the most volatile component of the gel formulation. In some aspects water may be the most volatile component of the gel formulation and the nicotine component of the gel formulation may be the second most volatile component of the gel formulation.

The gel composition preferably includes an aerosol-former. Ideally the aerosol-former is substantially resistant to thermal degradation at the operating temperature of the associated aerosol-generating device. Suitable aerosol-formers include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1 , 3-butanediol and glycerine; 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. Polyhydric alcohols or mixtures thereof, may be one or more of triethylene glycol, 1 , 3-butanediol and, glycerine (glycerol or propane-1 ,2 , 3-triol) or polyethylene glycol. The aerosol-former is preferably glycerol.

The gel composition may include a majority of an aerosol-former. The gel composition may include a mixture of water and the aerosol-former where the aerosol-former forms a majority (by weight) of the gel composition. The aerosol-former may form at least about 50 percent by weight of the gel composition. The aerosol-former may form at least about 60 percent by weight or at least about 65 percent by weight or at least about 70 percent by weight of the gel composition. The aerosol-former may form about 70 percent by weight to about 80 percent by weight of the gel composition. The aerosol-former may form about 70 percent by weight to about 75 percent by weight of the gel composition.

The gel composition may include a majority of glycerol. The gel composition may include a mixture of water and the glycerol where the glycerol forms a majority (by weight) of the gel composition. The glycerol may form at least about 50 percent by weight of the gel composition. The glycerol may form at least about 60 percent by weight or at least about 65 percent by weight or at least about 70 percent by weight of the gel composition. The glycerol may form about 70 percent by weight to about 80 percent by weight of the gel composition. The glycerol may form about 70 percent by weight to about 75 percent by weight of the gel composition.

The gel composition preferably includes at least one gelling agent. Preferably, the gel composition includes a total amount of gelling agents in a range from about 0.4 percent by weight to about 10 percent by weight. More preferably, the composition includes the gelling agents in a range from about 0.5 percent by weight to about 8 percent by weight. More preferably, the composition includes the gelling agents in a range from about 1 percent by weight to about 6 percent by weight. More preferably, the composition includes the gelling agents in a range from about 2 percent by weight to about 4 percent by weight. More preferably, the composition includes the gelling agents in a range from about 2 percent by weight to about 3 percent by weight. The term “gelling agent” refers to a compound that homogeneously, when added to a 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of about 0.3 percent by weight, forms a solid medium or support matrix leading to a gel. Gelling agents include, but are not limited to, hydrogen-bond crosslinking gelling agents, and ionic crosslinking gelling agents.

The gelling agent may include one or more biopolymers. The biopolymers may be formed of polysaccharides.

Biopolymers include, for example, gellan gums (native, low acyl gellan gum, high acyl gellan gums with low acyl gellan gum being preferred), xanthan gum, alginates (alginic acid), agar, guar gum, and the like. The composition may preferably include xanthan gum. The composition may include two biopolymers. The composition may include three biopolymers. The composition may include the two biopolymers in substantially equal weights. The composition may include the three biopolymers in substantially equal weights.

Preferably, the gel composition comprises at least about 0.2 percent by weight hydrogenbond crosslinking gelling agent. Alternatively or in addition, the gel composition preferably comprises at least about 0.2 percent by weight ionic crosslinking gelling agent. Most preferably, the gel composition comprises at least about 0.2 percent by weight hydrogen-bond crosslinking gelling agent and at least about 0.2 percent by weight ionic crosslinking gelling agent. The gel composition may comprise about 0.5 percent by weight to about 3 percent by weight hydrogenbond crosslinking gelling agent and about 0.5 percent by weight to about 3 percent by weight ionic crosslinking gelling agent, or about 1 percent by weight to about 2 percent by weight hydrogen-bond crosslinking gelling agent and about 1 percent by weight to about 2 percent by weight ionic crosslinking gelling agent. The hydrogen-bond crosslinking gelling agent and ionic crosslinking gelling agent may be present in the gel composition in substantially equal amounts by weight.

The term “hydrogen-bond crosslinking gelling agent” refers to a gelling agent that forms non-covalent crosslinking bonds or physical crosslinking bonds via hydrogen bonding. Hydrogen bonding is a type of electrostatic dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom and another very electronegative atom.

The hydrogen-bond crosslinking gelling agent may include one or more of a galactomannan, gelatin, agarose, or konjac gum, or agar. The hydrogen-bond crosslinking gelling agent may preferably include agar.

The gel composition preferably includes the hydrogen-bond crosslinking gelling agent in a range from about 0.3 percent by weight to about 5 percent by weight. Preferably the composition includes the hydrogen-bond crosslinking gelling agent in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the composition includes the hydrogen-bond crosslinking gelling agent in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include a galactomannan in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the galactomannan may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the galactomannan may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the galactomannan may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include a gelatin in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the gelatin may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the gelatin may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the gelatin may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include agarose in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the agarose may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the agarose may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the agarose may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include konjac gum in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the konjac gum may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the konjac gum may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the konjac gum may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include agar in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the agar may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the agar may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the agar may be in a range from about 1 percent by weight to about 2 percent by weight.

The term “ionic crosslinking gelling agent” refers to a gelling agent that forms non-covalent crosslinking bonds or physical crosslinking bonds via ionic bonding. Ionic crosslinking involves the association of polymer chains by noncovalent interactions. A crosslinked network is formed when multivalent molecules of opposite charges electrostatically attract each other giving rise to a crosslinked polymeric network.

The ionic crosslinking gelling agent may include low acyl gellan, pectin, kappa carrageenan, iota carrageenan or alginate. The ionic crosslinking gelling agent may preferably include low acyl gellan. The gel composition may include the ionic crosslinking gelling agent in a range from about 0.3 percent by weight to about 5 percent by weight. Preferably the composition includes the ionic crosslinking gelling agent in a range from about 0.5 percent by weight to about 3 percent by weight by weight. Preferably the composition includes the ionic crosslinking gelling agent in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include low acyl gellan in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the low acyl gellan may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the low acyl gellan may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the low acyl gellan may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include pectin in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the pectin may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the pectin may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the pectin may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include kappa carrageenan in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the kappa carrageenan may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the kappa carrageenan may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the kappa carrageenan may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include iota carrageenan in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the iota carrageenan may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the iota carrageenan may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the iota carrageenan may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include alginate in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the alginate may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the alginate may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the alginate may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include the hydrogen-bond crosslinking gelling agent and ionic crosslinking gelling agent in a ratio of about 3:1 to about 1 :3. Preferably the gel composition may include the hydrogen-bond crosslinking gelling agent and ionic crosslinking gelling agent in a ratio of about 2:1 to about 1 :2. Preferably the gel composition may include the hydrogen-bond crosslinking gelling agent and ionic crosslinking gelling agent in a ratio of about 1 :1. The gel composition may further include a viscosifying agent. The viscosifying agent combined with the hydrogen-bond crosslinking gelling agent and the ionic crosslinking gelling agent appears to surprisingly support the solid medium and maintain the gel composition even when the gel composition comprises a high level of glycerol.

The term “viscosifying agent” refers to a compound that, when added homogeneously into a 25°C, 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight., increases the viscosity without leading to the formation of a gel, the mixture staying or remaining fluid. Preferably the viscosifying agent refers to a compound that when added homogeneously into a 25°C 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight, increases the viscosity to at least 50 cPs, preferably at least 200 cPs, preferably at least 500 cPs, preferably at least 1000 cPs at a shear rate of 0.1 s’¹, without leading to the formation of a gel, the mixture staying or remaining fluid. Preferably the viscosifying agent refers to a compound that when added homogeneously into a 25°C 50 percent by weight water/50 percent by weight glycerol mixture, in an amount of 0.3 percent by weight, increases the viscosity at least 2 times, or at least 5 times, or at least 10 times, or at least 100 times higher than before addition, at a shear rate of 0.1 s’¹, without leading to the formation of a gel, the mixture staying or remaining fluid.

The viscosity values recited herein can be measured using a Brookfield RVT viscometer rotating a disc type RV#2 spindle at 25°C at a speed of 6 revolutions per minute (rpm).

The gel composition preferably includes the viscosifying agent in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the composition includes the viscosifying agent in a range from about 1 percent by weight to about 2 percent by weight.

The viscosifying agent may include one or more of xanthan gum, carboxymethyl-cellulose, microcrystalline cellulose, methyl cellulose, gum Arabic, guar gum, lambda carrageenan, or starch. The viscosifying agent may preferably include xanthan gum.

The gel composition may include xanthan gum in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the xanthan gum may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the xanthan gum may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the xanthan gum may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include carboxymethyl-cellulose in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the carboxymethyl-cellulose may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the carboxymethyl-cellulose may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the carboxymethyl-cellulose may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include microcrystalline cellulose in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the microcrystalline cellulose may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the microcrystalline cellulose may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the microcrystalline cellulose may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include methyl cellulose in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the methyl cellulose may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the methyl cellulose may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the methyl cellulose may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include gum Arabic in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the gum Arabic may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the gum Arabic may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the gum Arabic may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include guar gum in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the guar gum may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the guar gum may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the guar gum may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include lambda carrageenan in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the lambda carrageenan may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the lambda carrageenan may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the lambda carrageenan may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include starch in a range from about 0.2 percent by weight to about 5 percent by weight. Preferably the starch may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the starch may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the starch may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may further include a divalent cation. Preferably the divalent cation includes calcium ions, such as calcium lactate in solution. Divalent cations (such as calcium ions) may assist in the gel formation of compositions that include gelling agents such as the ionic crosslinking gelling agent, for example. The ion effect may assist in the gel formation. The divalent cation may be present in the gel composition in a range from about 0.1 to about 1 percent by weight, or about 0.5 percent by weight.

The gel composition may further include an acid. The acid may comprise a carboxylic acid. The carboxylic acid may include a ketone group. Preferably the carboxylic acid may include a ketone group having less than about 10 carbon atoms, or less than about 6 carbon atoms or less than about 4 carbon atoms, such as levulinic acid or lactic acid. Preferably this carboxylic acid has three carbon atoms (such as lactic acid). Lactic acid surprisingly improves the stability of the gel composition even over similar carboxylic acids. The carboxylic acid may assist in the gel formation. The carboxylic acid may reduce variation of the alkaloid compound concentration, or the cannabinoid compound concentration, or both the alkaloid compound concentration and the cannabinoid compound within the gel composition during storage. The carboxylic acid may reduce variation of the nicotine concentration within the gel composition during storage.

The gel composition may include a carboxylic acid in a range from about 0.1 percent by weight to about 5 percent by weight. Preferably the carboxylic acid may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the carboxylic acid may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the carboxylic acid may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include lactic acid in a range from about 0.1 percent by weight to about 5 percent by weight. Preferably the lactic acid may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the lactic acid may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the lactic acid may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition may include levulinic acid in a range from about 0.1 percent by weight to about 5 percent by weight. Preferably the levulinic acid may be in a range from about 0.5 percent by weight to about 3 percent by weight. Preferably the levulinic acid may be in a range from about 0.5 percent by weight to about 2 percent by weight. Preferably the levulinic acid may be in a range from about 1 percent by weight to about 2 percent by weight.

The gel composition preferably comprises some water. The gel composition is more stable when the composition comprises some water. Preferably the gel composition comprises at least about 1 percent by weight, or at least about 2 percent by weight., or at least about 5 percent by weight of water. Preferably the gel composition comprises at least about 10 percent by weight or at least about 15 percent by weight water.

Preferably the gel composition comprises between about 8 percent by weight to about 32 percent by weight water. Preferably the gel composition comprises from about 15 percent by weight to about 25 percent by weight water. Preferably the gel composition comprises from about 18 percent by weight to about 22 percent by weight water. Preferably the gel composition comprises about 20 percent by weight water.

Preferably, the aerosol-generating substrate comprises between about 150 mg and about 350 mg of the gel composition.

Preferably, in embodiments comprising a gel composition, the aerosol-generating substrate comprises a porous medium loaded with the gel composition. Advantages of a porous medium loaded with the gel composition is that the gel composition is retained within the porous medium, and this may aid manufacturing, storage or transport of the gel composition. It may assist in keeping the desired shape of the gel composition, especially during manufacture, transport, or use.

The term “porous” is used herein to refer to a material that provides a plurality of pores or openings that allow the passage of air through the material.

The porous medium may be any suitable porous material able to hold or retain the gel composition. Ideally the porous medium can allow the gel composition to move within it. In specific embodiments the porous medium comprises natural materials, synthetic, or semi-synthetic, or a combination thereof. In specific embodiments the porous medium comprises sheet material, foam, or fibres, for example loose fibres; or a combination thereof. In specific embodiments the porous medium comprises a woven, non-woven, or extruded material, or combinations thereof. Preferably the porous medium comprises, cotton, paper, viscose, PLA, or cellulose acetate, of combinations thereof. Preferably the porous medium comprises a sheet material, for example, cotton or cellulose acetate. In a particularly preferred embodiment, the porous medium comprises a sheet made from cotton fibres.

The porous medium used in the present invention may be crimped or shredded. In preferred embodiments, the porous medium is crimped. In alternative embodiments the porous medium comprises shredded porous medium. The crimping or shredding process can be before or after loading with the gel composition.

Crimping of the sheet material has the benefit of improving the structure to allow passageways through the structure. The passageways though the crimped sheet material assist in loading up gel, retaining gel and also for fluid to pass through the crimped sheet material. Therefore there are advantages of using crimped sheet material as the porous medium.

Shredding gives a high surface area to volume ratio to the medium thus able to absorb gel easily.

In specific embodiments the sheet material is a composite material. Preferably the sheet material is porous. The sheet material may aid manufacture of the tubular element comprising a gel. The sheet material may aid introducing an active agent to the tubular element comprising a gel. The sheet material may help stabilise the structure of the tubular element comprising a gel. The sheet material may assist transport or storage of the gel. Using a sheet material enables, or aids, adding structure to the porous medium for example by crimping of the sheet material.

The porous medium may be a thread. The thread may comprise for example cotton, paper or acetate tow. The thread may also be loaded with gel like any other porous medium. An advantage of using a thread as the porous medium is that it may aid ease of manufacturing.

The thread may be loaded with gel by any known means. The thread may be simply coated with gel, or the thread may be impregnated with gel. In the manufacture, the threads may be impregnated with gel and stored ready for use to be included in the assembly of a tubular element.

The porous medium loaded with the gel composition is preferably provided within a tubular element that forms a part of the aerosol-generating article. Ideally the tubular element may be longer in longitudinal length then in width but not necessarily as it may be one part of a multicomponent item that ideally will be longer in its longitudinal length then its width. Typically, the tubular element is cylindrical but not necessarily. For example, the tubular element may have an oval, polygonal like triangular or rectangular or random cross section.

The tubular element preferably comprises a first longitudinal passageway. The tubular element is preferably formed of a wrapper that defines the first longitudinal passageway. The wrapper is preferably a water-resistant wrapper. This water-resistant property the wrapper may be achieved by using a water-resistant material, or by treating the material of the wrapper. It may be achieved by treating one side or both sides of the wrapper. Being water- resistant would assist in not losing structure, stiffness or rigidity. It may also assist in preventing leaks of gel or liquid, especially when gels of a fluid structure are used.

Embodiments of the invention in which the rod of aerosol-generating substrate comprises a gel composition, as described above, preferably comprise an upstream segment upstream of the rod of aerosol-generating substrate. In this case, the upstream segment advantageously prevents physical contact with the gel composition. The upstream segment can also advantageously compensate for any potential reduction in RTD, for example, due to evaporation of the gel composition upon heating of the rod of aerosol-generating substrate during use.

In certain preferred embodiments, the aerosol-generating substrate may comprise or be in the form of solid aerosol-generating substrate. The solid aerosol-generating substrate may comprise nicotine, one or more cellulose based agents, one or more aerosol formers, and one or more carboxylic acids. The solid aerosol-generating substrate may have a total cellulose based agent content of at least 35 percent by weight, a total aerosol former content of greater than or equal to 45 percent by weight, and a total carboxylic acid content of at least 0.5 percent by weight. The one or more cellulose based agents may include one or more of cellulose based film-forming agents, cellulose based strengthening agents, and cellulose based binding agents. The solid aerosol-generating substrate may comprise one or more carboxylic acids that: (i) do not contain any non-carboxyl alkyl hydroxyl groups and do not contain any ketone groups; or (ii) have a pKa at 25°C in water of less than or equal to 3.5; or (iii) do not contain any non-carboxyl alkyl hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of less than or equal to 3.5. The one or more carboxylic acids may be selected from acetic acid, adipic acid, benzoic acid, citric acid, fumaric acid, maleic acid, malic acid, myristic acid, oxalic acid, salicylic acid, stearic acid, succinic acid, undecanoic acid, and C1-C10 saturated alkyl mono-carboxylic acids. The solid aerosol-generating substrate may further comprise one or more carboxylic acids selected from lactic acid and levulinic acid.

The solid aerosol-generating substrate may remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius. As described further below, this may advantageously reduce or eliminate crusting in aerosol-generating articles.

For example, the solid aerosol-generating substrate may remain solid when heated to a temperature of between 200 degrees Celsius and 320 degrees Celsius, between 220 degrees Celsius and 300 degrees Celsius, or between 240 degrees Celsius and 280 degrees Celsius.

The solid aerosol-generating substrate may be a solid aerosol-generating film.

As used herein, the term “film” is used to describe a solid aerosol-generating substrate having a thickness that is substantially less than the width or length thereof.

The term “exposed surface area of the film” is used herein to denote the cumulative surface area of the various surfaces of an aerosol-generating film that, during use, may become exposed to the gaseous airflow through the aerosol-generating article containing the film.

The “weight” of the aerosol-generating film of aerosol-generating articles according to the invention will generally correspond to the weight of the components of the corresponding filmforming composition minus the weight of water evaporated during the drying step. If a film is self- supporting, the film can be weighed on its own. If a film is disposed on a support, the film and the support may be weighed and the weight of the support, measured prior to deposition of the film, is subtracted from the combined weight of the film and the support.

Unless stated otherwise, percentages by weight of components of the aerosol-generating film recited herein are based on the total weight of the aerosol-generating film.

As used herein, the term “thickness” is used to describe the minimum dimension between opposite, substantially parallel surfaces of a solid aerosol-generating film. The thickness of the aerosol-generating film may substantially correspond to the thickness to which a corresponding film-forming composition is cast or extruded, as the cast or extruded film-forming composition substantially does not contract during drying, despite the loss of water.

The solid aerosol-generating film may have a thickness of greater than or equal to 0.05 millimetres, greater than or equal to 0.1 millimetres, greater than or equal to 0.2 millimetres, or greater than or equal to 0.3 millimetres. The solid aerosol-generating film may have a thickness of less than or equal to 1.2 millimetres, less than or equal to 1 millimetre, less than or equal to 0.8 millimetres, less than or equal to 0.6 millimetres, or less than or equal to 0.4 millimetres.

The solid aerosol-generating film may have a thickness of between 0.05 millimetres and

1.2 millimetres, between 0.05 millimetres and 1 millimetre, between 0.05 millimetres and 0.8 millimetres, between 0.05 millimetres and 0.6 millimetres, or between 0.05 millimetres and 0.4 millimetres.

The solid aerosol-generating film may have a thickness of between 0.1 millimetres and

1.2 millimetres, between 0.1 millimetres and 1 millimetre, between 0.1 millimetres and 0.8 millimetres, between 0.1 millimetres and 0.6 millimetres, or between 0.1 millimetres and 0.4 millimetres.

The solid aerosol-generating film may have a thickness of between 0.2 millimetres and

1.2 millimetres, between 0.2 millimetres and 1 millimetre, between 0.2 millimetres and 0.8 millimetres, between 0.2 millimetres and 0.6 millimetres, or between 0.2 millimetres and 0.4 millimetres.

The solid aerosol-generating film may have a thickness of between 0.3 millimetres and

1.2 millimetres, between 0.3 millimetres and 1 millimetre, between 0.3 millimetres and 0.8 millimetres, between 0.3 millimetres and 0.6 millimetres, or between 0.3 millimetres and 0.4 millimetres.

The solid aerosol-generating film may have a basis weight of greater than or equal to 85 grams per square metre, greater than or equal to 100 grams per square metre, greater than or equal to 120 grams per square metre, or greater than or equal to 140 grams per square metre.

The solid aerosol-generating film may have a basis weight of less than or equal to 300 grams per square metre, less than or equal to 280 grams per square metre, or less than or equal to 260 grams per square metre.

The solid aerosol-generating film may have a basis weight of between 85 grams per square metre and 300 grams per square metre, between 85 grams per square metre and 280 grams per square metre, or between 85 grams per square metre and 260 grams per square metre.

The solid aerosol-generating film may have a basis weight of between 100 grams per square metre and 300 grams per square metre, between 100 grams per square metre and 280 grams per square metre, or between 100 grams per square metre and 260 grams per square metre.

The solid aerosol-generating film may have a basis weight of between 120 grams per square metre and 300 grams per square metre, between 120 grams per square metre and 280 grams per square metre, or between 120 grams per square metre and 260 grams per square metre. The solid aerosol-generating film may have a basis weight of between 140 grams per square metre and 300 grams per square metre, between 140 grams per square metre and 280 grams per square metre, or between 140 grams per square metre and 260 grams per square metre.

The solid aerosol-generating film may be formed by any suitable method. For example, the solid aerosol-generating film may be formed by batch casting, continuous casting or extrusion.

The solid aerosol-generating film may be self-supporting. In other words, the properties of the solid aerosol-generating film may be such that, even if the solid aerosol-generating film is formed by casting a slurry onto a support surface, the solid aerosol-generating film can be separated from the support surface.

The solid aerosol-generating film may be disposed on a support or the solid aerosolgenerating film may be sandwiched between other materials. This may enhance the mechanical stability of the solid aerosol-generating film. For example, the solid aerosol-generating film may be disposed on a laminar support.

In some embodiments, the solid aerosol-generating film may be cut or otherwise divided into a plurality of strips or shreds that may be wrapped to form an aerosol-generating rod for inclusion in an aerosol-generating article.

In some embodiments, the solid aerosol-generating film may be gathered to form an aerosol-generating rod for inclusion in an aerosol-generating article.

The solid aerosol-generating film may be textured. This may facilitate gathering of the solid aerosol-generating film to form an aerosol-generating rod for inclusion in an aerosolgenerating article in some embodiments.

The term “textured” is used to describe a solid aerosol-generating film that has been crimped, embossed, debossed, perforated or otherwise deformed. Textured solid aerosolgenerating film may comprise a plurality of spaced-apart indentations, protrusions, perforations or a combination thereof.

The solid aerosol-generating film may be crimped.

As used herein, the term “crimped” is intended to be synonymous with the term “creped” and is used to describe a solid aerosol-generating film having a plurality of substantially parallel ridges or corrugations.

The crimped solid aerosol-generating film may have a plurality of ridges or corrugations substantially parallel to the cylindrical axis of the aerosol-generating rod. This may advantageously facilitate gathering of the crimped solid aerosol-generating film to form the aerosol-generating rod.

The solid aerosol-generating film may be textured using suitable known machinery for texturing filter tow, paper and other materials. The solid aerosol-generating film may be crimped using a crimping unit of the type described in CH-A-691156, which comprises a pair of rotatable crimping rollers. However, it will be appreciated that the solid aerosol-generating film may be textured using other suitable machinery and processes that deform or perforate the solid aerosol-generating film.

The solid aerosol-generating film may be incorporated directly into an aerosol-generating rod for inclusion in an aerosol-generating article.

The solid aerosol-generating film may be applied to a laminar support before being incorporated into an aerosol-generating rod for inclusion in an aerosol-generating article in some embodiments. For example, the solid aerosol-generating film may be applied to the surface of a sheet material. Suitable sheet materials for use as the laminar support include, but are not limited, to: paper; cardboard; and homogenised plant material. For example, the solid aerosol-generating film may be applied to a paper sheet, an aluminium coated paper sheet, or a polyethylene coated paper sheet.

The laminar support with the solid aerosol-generating film applied thereto may be cut or otherwise divided into a plurality of strips or shreds as described above.

The laminar support with the solid aerosol-generating film applied thereto may be gathered as described above.

The laminar support with the solid aerosol-generating film applied thereto may be textured as described above.

The solid aerosol-generating film may be applied to a tubular support before being incorporated into an aerosol-generating rod for inclusion in an aerosol-generating article in some embodiments. For example, the solid aerosol-generating film may be applied to the inner surface of a hollow tubular support.

Preferably, the solid aerosol-generating substrate may comprise nicotine.

As used herein, the term “nicotine” is used to describe nicotine, a nicotine base or a nicotine salt. In some embodiments in which the solid aerosol-generating substrate may comprise a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

The solid aerosol-generating substrate may comprise natural nicotine, or synthetic nicotine, or a combination of natural nicotine and synthetic nicotine.

The nicotine may comprise one or more nicotine salts. The one or more nicotine salts may be selected from the list consisting of nicotine lactate, nicotine citrate, nicotine pyruvate, nicotine bitartrate, nicotine benzoate, nicotine pectate, nicotine alginate, and nicotine salicylate.

The nicotine may comprise an extract of tobacco.

The solid aerosol-generating substrate may have a nicotine content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, greater than or equal to 1.5 percent by weight, or greater than or equal to 2 percent by weight. The solid aerosol-generating substrate may have a nicotine content of less than or equal to 10 percent by weight, less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight.

The solid aerosol-generating substrate may have a nicotine content of between 0.5 percent by weight and 10 percent by weight, between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a nicotine content of between 1 percent by weight and 10 percent by weight, between 1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a nicotine content of between 1.5 percent by weight and 10 percent by weight, between 1.5 percent by weight and 8 percent by weight, between 1 .5 percent by weight and 6 percent by weight, or between 1.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a nicotine content of between 2 percent by weight and 10 percent by weight, between 2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate comprises one or more aerosol formers.

The term “aerosol former” is used to describe a compound that, in use, facilitates formation of the aerosol, and that preferably is substantially resistant to thermal degradation at the operating temperature of an aerosol-generating article or aerosol-generating system comprising the solid aerosol-generating substrate.

Examples of suitable aerosol formers include: polyhydric alcohols, such as 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol; 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.

Preferably, the one or more aerosol formers comprise one or more polyhydric alcohols selected from 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol.

More preferably, the one or more aerosol formers comprise one or more or more polyhydric alcohols selected from glycerine and propylene glycol. Even more preferably, the one or more aerosol formers comprise glycerine.

Most preferably, the one or more aerosol formers may be glycerine.

The solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 45 percent by weight. The term “total aerosol former content” is used to describe the combined content of all aerosol formers in the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a total aerosol former content of greater than or equal to 46 percent by weight, greater than or equal to 48 percent by weight, greater than or equal to 50 percent by weight, or greater than or equal to 52 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of less than or equal to 62 percent by weight, less than or equal to 60 percent by weight, less than or equal to 58 percent by weight, less than or equal to 56 percent by weight, or less than or equal to 54 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of between 45 percent by weight and 62 percent by weight, between 45 percent by weight and 60 percent by weight, between 45 percent by weight and 58 percent by weight, between 45 percent by weight and 56 percent by weight, or between 45 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of between 46 percent by weight and 62 percent by weight, between 46 percent by weight and 60 percent by weight, between 46 percent by weight and 58 percent by weight, between 46 percent by weight and 56 percent by weight, or between 46 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of between 48 percent by weight and 62 percent by weight, between 48 percent by weight and 60 percent by weight, between 48 percent by weight and 58 percent by weight, between 48 percent by weight and 56 percent by weight, or between 48 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of between 50 percent by weight and 62 percent by weight, between 50 percent by weight and 60 percent by weight, between 50 percent by weight and 58 percent by weight, between 50 percent by weight and 56 percent by weight, or between 50 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total aerosol former content of between 52 percent by weight and 62 percent by weight, between 52 percent by weight and 60 percent by weight, between 52 percent by weight and 58 percent by weight, between 52 percent by weight and 56 percent by weight, or between 52 percent by weight and 54 percent by weight.

Preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of greater than or equal to 45 percent by weight, greater than or equal to 46 percent by weight, greater than or equal to 48 percent by weight, greater than or equal to 50 percent by weight, or greater than or equal to 52 percent by weight.

The term “total polyhydric alcohol content” is used to describe the combined content of all polyhydric alcohols in the solid aerosol-generating substrate. The solid aerosol-generating substrate may have a total polyhydric alcohol content of less than or equal to 62 percent by weight, less than or equal to 60 percent by weight, less than or equal to 58 percent by weight, less than or equal to 56 percent by weight, or less than or equal to 54 percent by weight.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of between 45 percent by weight and 62 percent by weight, between 45 percent by weight and 60 percent by weight, between 45 percent by weight and 58 percent by weight, between 45 percent by weight and 56 percent by weight, or between 45 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of between 46 percent by weight and 62 percent by weight, between 46 percent by weight and 60 percent by weight, between 46 percent by weight and 58 percent by weight, between 46 percent by weight and 56 percent by weight, or between 46 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of between 48 percent by weight and 62 percent by weight, between 48 percent by weight and 60 percent by weight, between 48 percent by weight and 58 percent by weight, between 48 percent by weight and 56 percent by weight, or between 48 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of between 50 percent by weight and 62 percent by weight, between 50 percent by weight and 60 percent by weight, between 50 percent by weight and 58 percent by weight, between 50 percent by weight and 56 percent by weight, or between 50 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total polyhydric alcohol content of between 52 percent by weight and 62 percent by weight, between 52 percent by weight and 60 percent by weight, between 52 percent by weight and 58 percent by weight, between 52 percent by weight and 56 percent by weight, or between 52 percent by weight and 54 percent by weight.

Preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols selected from 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol.

More preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols selected from glycerine and propylene glycol.

Most preferably, the solid aerosol-generating substrate comprises glycerine.

The solid aerosol-generating substrate may have a glycerine content of greater than or equal to 35 percent by weight, greater than or equal to 40 percent by weight, greater than or equal to 45 percent by weight, greater than or equal to 46 percent by weight, greater than or equal to 48 percent by weight, greater than or equal to 50 percent by weight, or greater than or equal to 52 percent by weight.

The solid aerosol-generating substrate may have a glycerine content of less than or equal to 62 percent by weight, less than or equal to 60 percent by weight, less than or equal to 58 percent by weight, less than or equal to 56 percent by weight, or less than or equal to 54 percent by weight.

The solid aerosol-generating substrate may have a glycerine content of between 35 percent by weight and 62 percent by weight, between 35 percent by weight and 60 percent by weight, between 35 percent by weight and 58 percent by weight, between 35 percent by weight and 56 percent by weight, or between 35 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total glycerine content of between 40 percent by weight and 62 percent by weight, between 40 percent by weight and 60 percent by weight, between 40 percent by weight and 58 percent by weight, between 40 percent by weight and 56 percent by weight, or between 40 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a glycerine content of between

45 percent by weight and 62 percent by weight, between 45 percent by weight and 60 percent by weight, between 45 percent by weight and 58 percent by weight, between 45 percent by weight and 56 percent by weight, or between 45 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a glycerine content of between

46 percent by weight and 62 percent by weight, between 46 percent by weight and 60 percent by weight, between 46 percent by weight and 58 percent by weight, between 46 percent by weight and 56 percent by weight, or between 46 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a glycerine content of between 48 percent by weight and 62 percent by weight, between 48 percent by weight and 60 percent by weight, between 48 percent by weight and 58 percent by weight, between 48 percent by weight and 56 percent by weight, or between 48 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total glycerine content of between 50 percent by weight and 62 percent by weight, between 50 percent by weight and 60 percent by weight, between 50 percent by weight and 58 percent by weight, between 50 percent by weight and 56 percent by weight, or between 50 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate may have a total glycerine content of between 52 percent by weight and 62 percent by weight, between 52 percent by weight and 60 percent by weight, between 52 percent by weight and 58 percent by weight, between 52 percent by weight and 56 percent by weight, or between 52 percent by weight and 54 percent by weight.

The solid aerosol-generating substrate comprises one or more carboxylic acids.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids. That is, the solid aerosol-generating substrate may comprise two or more carboxylic acids. For example, the solid aerosol-generating substrate may comprise two carboxylic acids, three carboxylic acids, four carboxylic acids, or five carboxylic acids.

It has surprisingly been found that inclusion of one or more carboxylic acids in the solid aerosol-generating substrate of aerosol-generating articles may advantageously improve the stability of the solid aerosol-generating substrate during storage of aerosol-generating articles. It has surprisingly been found that inclusion of one or more carboxylic acids in the solid aerosolgenerating substrate of aerosol-generating articles may advantageously improve the stability of nicotine in the solid aerosol-generating substrate during storage of aerosol-generating articles. In particular, it has surprisingly been found that inclusion of one or more carboxylic acids in the solid aerosol-generating substrate of aerosol-generating articles may advantageously inhibit corrosion of components of aerosol-generating articles. In particular, it has surprisingly been found that inclusion of one or more carboxylic acids in the solid aerosol-generating substrate of aerosolgenerating articles may advantageously inhibit corrosion of metal components of aerosolgenerating articles. In particular, it has surprisingly been found that inclusion of one or more carboxylic acids in the solid aerosol-generating substrate of aerosol-generating articles may advantageously inhibit corrosion of the susceptor of aerosol-generating articles. In some embodiments, the susceptor is in direct contact with the aerosol-generating substrate.

Without wishing to be bound by theory, it is believed that, when included in the solid aerosol-generating substrate, carboxylic acids that do not contain any non-carboxyl alkyl hydroxyl groups are less prone to oxidise other components of aerosol-generating articles than carboxylic acids that do contain non-carboxyl alkyl hydroxyl groups. Without wishing to be bound by theory, it is believed that when included in the solid aerosol-generating substrate, carboxylic acids that do not contain any ketone groups are less prone to oxidise other components of aerosolgenerating articles than carboxylic acids that do contain ketone groups. It is believed that inclusion of one or more carboxylic acids that do not contain any non-carboxyl alkyl hydroxyl groups and do not contain any ketone groups in the solid aerosol-generating substrate thereby inhibits corrosion of components of aerosol-generating articles.

Without wishing to be bound by theory, it is believed that, when included in the solid aerosol-generating substrate, carboxylic acids having a pKa of less than or equal to 3.5 are less prone to oxidise other components of aerosol-generating articles than carboxylic acids having pKa of greater than 3.5. It is believed that inclusion of one or more carboxylic acids having a pKa of less than or equal to 3.5 in the solid aerosol-generating substrate thereby inhibits corrosion of components of aerosol-generating articles.

The solid aerosol-generating substrate may comprise one or more carboxylic acids that: (i) do not contain any non-carboxyl alkyl hydroxyl groups and do not contain any ketone groups; or (ii) have a pKa at 25°C in water of less than or equal to 3.5; or (iii) do not contain any non- carboxyl alkyl hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of less than or equal to 3.5.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids that do not contain any non-carboxyl alky hydroxyl groups and do not contain any ketone groups. For example, the solid aerosol-generating substrate may comprise benzoic acid and succinic acid. The solid aerosol-generating substrate may comprise one or more carboxylic acids having a pKa at 25°C in water of less than or equal to 3.5.

As used herein with reference to the invention, the term “carboxylic acids having a pKa at 25°C in water of less than or equal to 3.5” is used to describe monoprotic carboxylic acids having a pKa at 25°C in water of less than or equal to 3.5 and polyprotic carboxylic acids having a pKa1 at 25°C in water of less than or equal to 3.5.

For example, the solid aerosol-generating substrate may comprise one or more carboxylic acids selected from citric acid, fumaric acid, maleic acid, malic acid, oxalic acid, and salicylic acid.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids having a pKa at 25°C in water of less than or equal to 3.5. For example, the solid aerosol-generating substrate may comprise citric acid and malic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids that do not contain any non-carboxyl alky hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of less than or equal to 3.5. For example, the solid aerosol-generating substrate may comprise one or more carboxylic acids selected from fumaric acid, maleic acid, oxalic acid, and salicylic acid.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids that do not contain any non-carboxyl alky hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of less than or equal to 3.5. For example, the solid aerosol-generating substrate may comprise fumaric acid and maleic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids having a pKa at 25°C in water of greater than or equal to 3.6.

As used herein with reference to the invention, the term “carboxylic acids having a pKa at 25°C in water of greater than or equal to 3.6” is used to describe monoprotic carboxylic acids having a pKa at 25°C in water of greater than or equal to 3.6 and polyprotic carboxylic acids having a pKa1 at 25°C in water of greater than or equal to 3.6.

The solid aerosol-generating substrate may comprise one or more carboxylic acids that do not contain any non-carboxyl alky hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of greater than or equal to 3.6. For example, the solid aerosolgenerating substrate may comprise one or more carboxylic acids selected from acetic acid, adipic acid, benzoic acid, and succinic acid.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids that do not contain any non-carboxyl alky hydroxyl groups, do not contain any ketone groups, and have a pKa at 25°C in water of greater than or equal to 3.6. For example, the solid aerosolgenerating substrate may comprise acetic acid and benzoic acid.

The solid aerosol-generating substrate may further comprise one or more carboxylic acids that contain a non-carboxyl alky hydroxyl group and have a pKa at 25°C in water of greater than or equal to 3.6. For example, the solid aerosol-generating substrate may further comprise lactic acid.

The solid aerosol-generating substrate may further comprise one or more carboxylic acids that contain a ketone group and have a pKa at 25°C in water of greater than or equal to 3.6. For example, the solid aerosol-generating substrate may further comprise levulinic acid.

The solid aerosol-generating substrate may comprise a plurality of carboxylic acids having a pKa at 25°C in water of greater than or equal to 3.6. For example, the solid aerosol-generating substrate may comprise benzoic acid and lactic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids having a pKa at 25°C in water of less than or equal to 3.5 and one or more carboxylic acids having a pKa at 25°C in water of greater than or equal to 3.6.

For example, the solid aerosol-generating substrate may comprise one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid and one or more carboxylic acids selected from acetic acid, benzoic acid, lactic acid, and levulinic acid.

For example, the solid aerosol-generating substrate may comprise fumaric acid and one or more carboxylic acids selected from acetic acid, benzoic acid, lactic acid, and levulinic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from acetic acid, adipic acid, benzoic acid, citric acid, fumaric acid, maleic acid, malic acid, myristic acid, oxalic acid, salicylic acid, stearic acid, succinic acid, undecanoic acid, and C1- C10 saturated alkyl mono-carboxylic acids.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from acetic acid, adipic acid, benzoic acid, citric acid, fumaric acid, maleic acid, malic acid, myristic acid, oxalic acid, salicylic acid, stearic acid, succinic acid, and undecanoic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from acetic acid, adipic acid, benzoic acid, citric acid, fumaric acid, maleic acid, myristic acid, oxalic acid, salicylic acid, stearic acid, succinic acid, and undecanoic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from acetic acid, benzoic acid, citric acid, fumaric acid, maleic acid, and malic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from acetic acid, benzoic acid, citric acid, fumaric acid, and maleic acid.

The solid aerosol-generating substrate may comprise one or more carboxylic acids selected from fumaric acid, maleic acid, and malic acid.

Preferably, the solid aerosol-generating substrate comprises one or more carboxylic acids selected from fumaric acid and maleic acid.

More preferably, the solid aerosol-generating substrate comprises fumaric acid.

The solid aerosol-generating substrate may further comprise one or more carboxylic acids selected from lactic acid and levulinic acid. Advantageously, including one or more carboxylic acids in the aerosol-generating substrate may create a nicotine salt. Advantageously, the present inventors have found that lactic acid and levulinic acid are particularly good carboxylic acids for creating nicotine salts.

The solid aerosol-generating substrate has a total carboxylic acid content of greater than or equal to 0.5 percent by weight.

The term “total carboxylic acid content” is used to describe the combined content of all carboxylic acids in the solid aerosol-generating substrate. For example, where the solid aerosolgenerating substrate comprises a plurality of carboxylic acids consisting of benzoic acid and fumaric acid, the term “total carboxylic acid content” describes the combined benzoic acid content and fumaric acid content of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a total carboxylic acid content of greater than or equal to 1 percent by weight, greater than or equal to 1 .5 percent by weight, or greater than or equal to 2 percent by weight.

The solid aerosol-generating substrate may have a total carboxylic acid content of less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight.

The solid aerosol-generating substrate may have a total carboxylic acid content of between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a total carboxylic acid content of between 1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a total carboxylic acid content of between 1.5 percent by weight and 8 percent by weight, between 1.5 percent by weight and 6 percent by weight, or between 1.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a total carboxylic acid content of between 2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be greater than or equal to 0.5:1 , greater than or equal to 1 :1 , greater than or equal to 1.5:1 , or greater than or equal to 2: 1.

The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be less than or equal to 5: 1 , less than or equal to 4.5: 1 , less than or equal to 4: 1 , or less than or equal to 3.5:1.

The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 0.5:1 and 5:1 , between 0.5:1 and 4.5:1 , between 0.5:1 and 4:1 , or between 0.5:1 and 3.5:1. The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 1 :1 and 5:1 , between 1 :1 and 4.5:1 , between 1 :1 and 4:1 , or between 1 :1 and 3.5:1.

The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 1.5:1 and 5:1 , between 1.5:1 and 4.5:1 , between 1.5:1 and 4:1 , or between 1.5:1 and 3.5:1.

The molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 2:1 and 5:1 , between 2:1 and 4.5:1 , between 2:1 and 4:1 , or between 2:1 and 3.5:1.

The solid aerosol-generating substrate may have a fumaric acid content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, greater than or equal to 1.5 percent by weight, or greater than or equal to 2 percent by weight.

The solid aerosol-generating substrate may have a fumaric acid content of less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight.

The solid aerosol-generating substrate may have a fumaric acid content of between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a fumaric acid content of between

1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a fumaric acid content of between 1 .5 percent by weight and 8 percent by weight, between 1 .5 percent by weight and 6 percent by weight, or between 1.5 percent by weight and 4 percent by weight.

2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be greater than or equal to 0.5:1 , greater than or equal to 1 :1 , greater than or equal to 1.5:1 , or greater than or equal to 2:1 .

The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be less than or equal to 4:1 , or less than or equal to 3.5:1 , less than or equal to 3:1 , or less than or equal to 2.5:1.

The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be between 0.5:1 and 4:1 , between 0.5:1 and 3.5:1 , between 0.5:1 and 3:1 , or between 0.5:1 and 2.5:1. The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be between 1 :1 and 4:1 , between 1 :1 and 3.5:1 , between 1 :1 and 3:1 , or between 1 :1 and 2.5:1.

The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be between 1.5:1 and 4:1 , between 1.5:1 and 3.5:1 , between 1.5:1 and 3:1 , or between 1.5:1 and 2.5:1.

The molar ratio of fumaric acid to nicotine in the solid aerosol-generating substrate may be between 2:1 and 4:1 , between 2:1 and 3.5:1 , between 2:1 and 3:1 , or between 2:1 and 2.5:1.

The solid aerosol-generating substrate comprises one or more cellulose based agents.

The term “cellulose based agent” is used to describe a cellulosic substance. Examples of cellulose based agents include cellulose based film-forming agents, cellulose based strengthening agents and cellulose based binding agents.

The solid aerosol-generating substrate may comprise a plurality of cellulose based agents. That is, the solid aerosol-generating substrate may comprise two or more cellulose based agents. For example, the solid aerosol-generating substrate may comprise two cellulose based agents, three cellulose based agents, four cellulose based agents, or five cellulose based agents.

The solid aerosol-generating substrate may have a total cellulose based agent content of greater than or equal to 25 percent by weight, or greater than or equal to 30 percent by weight.

The term “total cellulose based agent content” is used to describe the combined content of all cellulose based agents in the solid aerosol-generating substrate. For example, where the solid aerosol-generating substrate comprises a plurality of cellulose based agents consisting of a cellulose based film-forming agent, a cellulose based strengthening agent, and a cellulose based binding agent, the term “total cellulose based agent content” describes the combined cellulose based film-forming agent content, cellulose based strengthening agent content, and cellulose based binding agent content of the solid aerosol-generating substrate.

Preferably, the solid aerosol-generating substrate has a total cellulose based agent content of greater than or equal to 35 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of greater than or equal to 36 percent by weight, greater than or equal to 38 percent by weight, or greater than or equal to 40 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of less than or equal to 52 percent by weight, less than or equal to 50 percent by weight, less than or equal to 48 percent by weight, less than or equal to 46 percent by weight, or less than or equal to 44 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of between 35 percent by weight and 52 percent by weight, between 35 percent by weight and 50 percent by weight, between 35 percent by weight and 48 percent by weight, between 35 percent by weight and 46 percent by weight, or between 35 percent by weight and 44 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of between 36 percent by weight and 52 percent by weight, between 36 percent by weight and 50 percent by weight, between 36 percent by weight and 48 percent by weight, between

36 percent by weight and 46 percent by weight, or between 36 percent by weight and 44 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of between 38 percent by weight and 52 percent by weight, between 38 percent by weight and 50 percent by weight, between 38 percent by weight and 48 percent by weight, between 38 percent by weight and 46 percent by weight, or between 38 percent by weight and 44 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based agent content of between 40 percent by weight and 52 percent by weight, between 40 percent by weight and 50 percent by weight, between 40 percent by weight and 48 percent by weight, between 40 percent by weight and 46 percent by weight, or between 40 percent by weight and 44 percent by weight.

The solid aerosol-generating substrate may comprise one or more cellulose based filmforming agents.

The term “cellulose based film-forming agent” is used to describe a cellulosic polymer capable, by itself or in the presence of an auxiliary thickening agent, of forming a continuous film.

Advantageously, the solid aerosol-generating substrate may comprise one or more cellulose based film-forming agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), hydroxyethyl cellulose (HEC), hydroxyethyl methylcellulose (HEMC), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and methylcellulose (MC).

More advantageously, the solid aerosol-generating substrate may comprise one or more cellulose based film-forming agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC).

Most advantageously, the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents selected from carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC).

Preferably, the solid aerosol-generating substrate comprises carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC).

Most preferably, the solid aerosol-generating substrate comprises hydroxypropyl methylcellulose (HPMC).

The one or more cellulose based film-forming agents may act as a binding agent for the solid aerosol-generating substrate. The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of greater than or equal to 15 percent by weight, greater than or equal to 20 percent by weight, or greater than or equal to 25 percent by weight.

As used herein, the term “total cellulose based film-forming agent content” is used to describe the combined content of all cellulose based film-forming agents in the solid aerosolgenerating substrate.

The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of less than or equal to 40 percent by weight, less than or equal to 35 percent by weight, or less than or equal to 30 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 15 percent by weight and 40 percent by weight, between 15 percent by weight and 35 percent by weight, or between 15 percent by weight and 30 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 20 percent by weight and 40 percent by weight, between 20 percent by weight and 35 percent by weight, or between 20 percent by weight and 30 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 25 percent by weight and 40 percent by weight, between 25 percent by weight and 35 percent by weight, or between 25 percent by weight and 30 percent by weight.

Inclusion of hydroxypropylmethyl cellulose in the solid aerosol-generating substrate may advantageously facilitate manufacturing of the solid aerosol-generating substrate. For example, hydroxypropylmethyl cellulose may advantageously reduce the overall viscosity of a slurry of components of the solid aerosol-generating substrate produced during manufacturing of the solid aerosol- generating substrate. A lower viscosity slurry may flow more easily and be easier to mix, transfer and handle during the manufacturing process

Hydroxypropylmethyl cellulose may advantageously act as a binding agent for the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of greater than or equal to 14 percent by weight, greater than or equal to 16 percent by weight, greater than or equal to 18 percent by weight, or greater than or equal to 20 percent by weight.

The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of less than or equal to 40 percent by weight, less than or equal to 35 percent by weight, less than or equal to 30 percent by weight, or less than or equal to 25 percent by weight.

The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of between 14 percent by weight and 40 percent by weight, between 14 percent by weight and 35 percent by weight, between 14 percent by weight and 30 percent by weight, or between 14 percent by weight and 25 percent by weight. The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of between 16 percent by weight and 40 percent by weight, between 16 percent by weight and 35 percent by weight, between 16 percent by weight and 30 percent by weight, or between 16 percent by weight and 25 percent by weight.

The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of between 18 percent by weight and 40 percent by weight, between 18 percent by weight and 35 percent by weight, between 18 percent by weight and 30 percent by weight, or between 18 percent by weight and 25 percent by weight.

The solid aerosol-generating substrate may have a hydroxypropylmethyl cellulose content of between 20 percent by weight and 40 percent by weight, between 20 percent by weight and 35 percent by weight, between 20 percent by weight and 30 percent by weight, or between 20 percent by weight and 25 percent by weight.

Inclusion of carboxymethyl cellulose in the solid aerosol-generating substrate may advantageously reduce or eliminate crusting in aerosol-generating articles.

As used herein, the term “crusting” is used to describe the formation of a solid layer on a component of the aerosol-generating article.

Crusting may occur due to a component of the solid aerosol-generating substrate melting and then re-solidify around a component of the aerosol-generating article during use thereof. Crusting may be a particular problem in aerosol-generating articles which contain a susceptor in direct contact with the solid aerosol-forming substrate. If a crust is formed on the susceptor, the crusted susceptor may become less effective at heating the solid aerosol-generating substrate. This may disadvantageously lead to one or both of reduced delivery of nicotine to a user and reduced formation of aerosol from the solid aerosol-generating substrate.

The solid aerosol-generating substrate may comprise sodium carboxymethyl cellulose.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of greater than or equal to 2 percent by weight, greater than or equal to 3 percent by weight, greater than or equal to 4 percent by weight, or greater than or equal to 5 percent by weight.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of less than or equal to 12 percent by weight, less than or equal to 10 percent by weight, less than or equal to 8 percent by weight, or less than or equal to 6 percent by weight.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of between 2 percent by weight and 12 percent by weight, between 2 percent by weight and 10 percent by weight, between 2 percent by weight and 8 percent by weight, or between 2 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of between 3 percent by weight and 12 percent by weight, between 3 percent by weight and 10 percent by weight, between 3 percent by weight and 8 percent by weight, or between 3 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of between 4 percent by weight and 12 percent by weight, between 4 percent by weight and 10 percent by weight, between 4 percent by weight and 8 percent by weight, or between 4 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may have a carboxymethyl cellulose content of between 5 percent by weight and 12 percent by weight, between 5 percent by weight and 10 percent by weight, between 5 percent by weight and 8 percent by weight, or between 5 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may comprise one or more cellulose based strengthening agents.

Inclusion of one or more cellulose based strengthening agents in the solid aerosolgenerating substrate may advantageously increase the tensile strength of the solid aerosolgenerating substrate. In particular, where the solid aerosol-generating substrate is a solid aerosol-generating film, inclusion of one or more cellulose based strengthening agents in the solid aerosol-generating substrate may advantageously increase the tensile strength of the solid aerosol-generating film. A solid aerosol-generating substrate having a higher tensile strength may advantageously be less likely to deteriorate or break during manufacture and storage.

Advantageously, the solid aerosol-generating substrate may comprise one or more cellulose based strengthening agents selected from cellulose fibres, cellulose powder, and microcrystalline cellulose (MCC).

Preferably, the solid aerosol-generating substrate comprises cellulose fibres. Cellulose fibres may be particularly effective at increasing the tensile strength of the solid aerosolgenerating substrate.

The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

The term “total cellulose based strengthening agent content” is used to describe the combined content of all cellulose based strengthening agents in the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight. The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of greater than or equal to 0.2 millimetres, greater than or equal to 0.5 millimetres, greater than or equal to 0.7 millimetres, or greater than or equal to 0.9 millimetres.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of less than or equal to 2 millimetres, less than or equal to 1.8 millimetres, less than or equal to 1 .6 millimetres, or less than or equal to 1 .4 millimetres.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of between 0.2 millimetres and 2.0 millimetres, between 0.2 millimetres and 1 .8 millimetres, between 0.2 millimetres and 1.6 millimetres, or between 0.2 millimetres and 1.4 millimetres.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of between 0.5 millimetres and 2.0 millimetres, between 0.5 millimetres and 1 .8 millimetres, between 0.5 millimetres and 1.6 millimetres, or between 0.5 millimetres and 1.4 millimetres.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of between 0.7 millimetres and 2.0 millimetres, between 0.7 millimetres and 1 .8 millimetres, between 0.7 millimetres and 1.6 millimetres, or between 0.7 millimetres and 1.4 millimetres.

The solid aerosol-generating substrate may comprise cellulose fibres having a length of between 0.9 millimetres and 2.0 millimetres, between 0.9 millimetres and 1 .8 millimetres, between 0.9 millimetres and 1.6 millimetres, or between 0.9 millimetres and 1.4 millimetres.

The solid aerosol-generating substrate may have a cellulose fibre content of greater than or equal to 2 percent by weight, greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

The solid aerosol-generating substrate may have a cellulose fibre content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose fibre content of between 2 percent by weight and 30 percent by weight, between 2 percent by weight and 25 percent by weight, or between 2 percent by weight and 20 percent by weight. The solid aerosol-generating substrate may have a cellulose fibre content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose fibre content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose fibre content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may comprise microcrystalline cellulose having a D50 size of greater than or equal to 5 micrometres, greater than or equal to 10 micrometres, or greater than or equal to 15 micrometres.

As used herein, the term “D50 size” describes the median particle size of a particulate material. The D50 size is the particle size which splits the distribution in half, where half of the particles are larger than the D50 size and half of the particles are smaller than the D50 size. The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions.

The solid aerosol-generating substrate may comprise microcrystalline cellulose having a D50 size of less than or equal to 100 micrometres, less than or equal to 90 micrometres, or less than or equal to 80 micrometres.

The solid aerosol-generating substrate may comprise microcrystalline cellulose having a D50 size of between 5 micrometres and 100 micrometres, between 5 micrometres and 90 micrometres, or between 5 micrometres and 80 micrometres.

The solid aerosol-generating substrate may comprise microcrystalline cellulose having a D50 size of between 10 micrometres and 100 micrometres, between 10 micrometres and 90 micrometres, or between 10 micrometres and 80 micrometres.

The solid aerosol-generating substrate may comprise microcrystalline cellulose having a D50 size of between 15 micrometres and 100 micrometres, between 15 micrometres and 90 micrometres, or between 150 micrometres and 80 micrometres.

The solid aerosol-generating substrate may have a microcrystalline cellulose content of greater than or equal to 2 percent by weight, greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

The solid aerosol-generating substrate may have a microcrystalline cellulose content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight. The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 2 percent by weight and 30 percent by weight, between 2 percent by weight and 25 percent by weight, or between 2 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may comprise cellulose powder having a D50 size of greater than or equal to 25 micrometres, greater than or equal to 30 micrometres, or greater than or equal to 35 micrometres.

The solid aerosol-generating substrate may comprise cellulose powder having a D50 size of less than or equal to 250 micrometres, less than or equal to 225 micrometres, or less than or equal to 200 micrometres.

The solid aerosol-generating substrate may comprise cellulose powder having a D50 size of between 25 micrometres and 250 micrometres, between 25 micrometres and 225 micrometres, or between 25 micrometres and 200 micrometres.

The solid aerosol-generating substrate may comprise cellulose powder having a D50 size of between 30 micrometres and 250 micrometres, between 30 micrometres and 225 micrometres, or between 30 micrometres and 200 micrometres.

The solid aerosol-generating substrate may comprise cellulose powder having a D50 size of between 35 micrometres and 250 micrometres, between 35 micrometres and 225 micrometres, or between 35 micrometres and 200 micrometres.

The solid aerosol-generating substrate may have a cellulose powder content of greater than or equal to 2 percent by weight, greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

The solid aerosol-generating substrate may have a cellulose powder content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose powder content of between 2 percent by weight and 30 percent by weight, between 2 percent by weight and 25 percent by weight, or between 2 percent by weight and 20 percent by weight. The solid aerosol-generating substrate may have a cellulose powder content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose powder content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may have a cellulose powder content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

The solid aerosol-generating substrate may comprise water.

The solid aerosol-generating substrate may have a water content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, greater than or equal to 15 percent by weight, or greater than or equal to 17 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a water content of less than or equal to 35 percent by weight, less than or equal to 30 percent by weight, or less than or equal to 25 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a water content of between 5 percent by weight and 35 percent by weight, between 5 percent by weight and 30 percent by weight, or between 5 percent by weight and 25 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a water content of between 10 percent by weight and 35 percent by weight, between 10 percent by weight and 30 percent by weight, or between 10 percent by weight and 25 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a water content of between 15 percent by weight and 35 percent by weight, between 15 percent by weight and 30 percent by weight, or between 15 percent by weight and 25 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a water content of between 17 percent by weight and 35 percent by weight, between 17 percent by weight and 30 percent by weight, or between 17 percent by weight and 25 percent by weight based on the total weight of the solid aerosol-generating substrate.

The solid aerosol-generating substrate may comprise one or more non-cellulose based thickening agents.

As used herein, the term “non-cellulose based thickening agent” is used to describe a non- cellulosic substance that, when added to an aqueous or non-aqueous liquid composition, increases the viscosity of the liquid composition without substantially modifying its other properties. The one or more non-cellulose based thickening agents may increase stability, and improve suspension of components in the liquid composition. A thickening agent may also be referred to as a “thickener” or a “rheology modifier” or “viscosifying agent”.

The solid aerosol-generating substrate may comprise one or more non-cellulose based thickening agents selected from alginates, gellan gum, guar gum, gum arabic, locust bean gum, pectins, starches, and xanthan gum.

The solid aerosol-generating substrate may not comprise iota-carrageenan or kappa- carrageenan. Solid aerosol-generating substrates that do not comprise iota-carrageenan or kappa-carrageenan may advantageously remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius. This may advantageously reduce or eliminate crusting in aerosol-generating articles in which a susceptor is in direct contact with the substrate.

The solid aerosol-generating substrate may not comprise agar. Solid aerosol-generating substrates that do not agar may advantageously remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius. This may advantageously reduce or eliminate crusting in aerosol-generating articles in which a susceptor is in direct contact with the substrate.

The solid aerosol-generating substrate may have a total non-cellulose based thickening agent content of greater than or equal to 1 percent by weight, greater than or equal to 2 percent by weight, or greater than or equal to 3 percent by weight.

As used herein, the term “total non-cellulose based thickening agent content” is used to describe the combined content of all non-cellulose based thickening agents in the solid aerosolgenerating substrate.

The solid aerosol-generating substrate may have a total non-cellulose based thickening agent content of less than or equal to 10 percent by weight, less than or equal to 8 percent by weight, or less than or equal to 6 percent by weight.

The solid aerosol-generating substrate may have a total non-cellulose based thickening agent content of between 1 percent by weight and 10 percent by weight, between 1 percent by weight and 8 percent by weight, or between 1 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may have a total non-cellulose based thickening agent content of between 2 percent by weight and 10 percent by weight, between 2 percent by weight and 8 percent by weight, or between 2 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may have a total non-cellulose based thickening agent content of between 3 percent by weight and 10 percent by weight, between 3 percent by weight and 8 percent by weight, or between 3 percent by weight and 6 percent by weight.

The solid aerosol-generating substrate may comprise one or more flavourants.

Suitable flavourants are known in the art and include, but are not limited to, menthol. As used herein, the term “menthol” is used to describe the compound 2-isopropyl-5- methylcyclohexanol in any of its isomeric forms.

As used herein, the term “total flavourant content” is used to describe the combined content of all flavourants in the solid aerosol-generating substrate.

The solid aerosol-generating substrate may have a total flavourant content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, greater than or equal to 2 percent by weight, or greater than or equal to 3 percent by weight.

The solid aerosol-generating substrate may have a total flavourant content of less than or equal to 6 percent by weight, less than or equal to 5 percent by weight, or less than or equal to 4 percent by weight.

The solid aerosol-generating substrate may have a total flavourant content of between 0.5 percent by weight and 6 percent by weight, between 0.5 percent by weight and 5 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may have a total flavourant content of between

1 percent by weight and 6 percent by weight, between 1 percent by weight and 5 percent by weight, or between 1 percent by weight and 4 percent by weight.

2 percent by weight and 6 percent by weight, between 2 percent by weight and 5 percent by weight, or between 2 percent by weight and 4 percent by weight.

3 percent by weight and 6 percent by weight, between 3 percent by weight and 5 percent by weight, or between 3 percent by weight and 4 percent by weight.

The solid aerosol-generating substrate may be a substantially tobacco-free solid aerosolgenerating substrate.

As used herein, the term “substantially tobacco-free solid aerosol-generating substrate” is used to describe a solid aerosol-generating substrate having a tobacco content of less than 1 percent by weight. For example, the solid aerosol-generating substrate may have a tobacco content of less than 0.75 percent by weight, less than 0.5 percent by weight, or less than 0.25 percent by weight.

The solid aerosol-generating substrate may be a tobacco-free aerosol-generating film.

The term “tobacco-free solid aerosol-generating substrate” is used to describe a solid aerosol-generating substrate having a tobacco content of 0 percent by weight.

In a particularly preferred embodiment, the solid aerosol-generating substrate is a solid aerosol-generating film comprising: glycerine in an amount of between 35 percent by weight and 62 percent by weight; carboxymethyl cellulose in an amount of between 2 percent by weight and 12 percent by weight; hydroxypropylmethyl cellulose in an amount of between 14 percent by weight and 40 percent by weight; a total cellulose based strengthening agent content in an amount of between 2 percent by weight and 30 percent by weight; a total carboxylic acid content in an amount of between 0.5 percent by weight and 8 percent by weight; nicotine in an amount of between 0.5 percent by weight and 10 percent by weight; and water in an amount of between 5 percent by weight and 35 percent by weight.

In another embodiment, the aerosol-generating substrate may comprise thermally conductive particles. The aerosol-generating substrate may comprise, on a dry weight basis, between 10 and 90 weight percent [wt %] thermally conductive particles. The aerosol-generating substrate may comprise, on a dry weight basis, between 7 and 60 wt % of an aerosol former. The aerosol-generating substrate may comprise, on a dry weight basis, between 2 and 20 wt % of fibres. The aerosol-generating substrate may comprise, on a dry weight basis, between 2 and 10 wt % of a binder. Each of the thermally conductive particles may consist of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond.

Where 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, 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-generating substrate. The increased thermal conductivity of the substrate may provide a more even temperature distribution throughout the substrate during use. This may result in a greater proportion of the aerosol-generating substrate reaching a sufficiently high temperature to release volatile compounds, and thus a higher usage efficiency of the aerosolgenerating substrate. Further, the increased thermal conductivity of the substrate may allow a heater, for example a heating blade configured to heat the substrate, to operate at a lower temperature and thus require less power. Further still, the increased thermal conductivity of the substrate may allow a heater to heat the substrate to a temperature in which volatile compounds are released in less time. Thus, the increased thermal conductivity may reduce the time required to form an inhalable aerosol for a user.

Advantageously, one or both of the fibres and the binder may increase a tensile strength of the aerosol-generating substrate. The increased tensile strength may allow the production of a sheet of the aerosol-generating substrate which does not easily tear. The increased tensile strength may allow the production of a sheet of the aerosol-generating substrate using existing production machinery. The aerosol-generating 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 a moisture content of the substrate is between 0 and 20, or 5 and 15, for example around 10%. This thermal conductivity may be measured when the substrate comprises between 0 and 20, or 5 and 15, for example around 10 wt % water. The moisture or water content of the substrate may be measured using a titration method. The moisture or water content of the substrate may be measured using the Karl Fisher 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, for example artificial diamond particles. Advantageously, such materials may 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 centimetre cubed (g I 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 centimetre cubed (g I 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 centimetre cubed (g I cm3).

Optionally, where 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 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, where 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, aluminium nitride, aluminium, 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 aluminium nitride particles. Optionally, some or all of the thermally conductive particles are aluminium 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 relatively high thermal conductivities.

The thermally conductive particles may each have a “particle size”. The meaning of the term “particle size” and a method of measuring particle size is set out later.

The thermally conductive particles may be characterised by a particle size distribution. The particle size distribution may have number D10, D50 and D90 particle sizes. The number D10 particle size is defined such that 10% of the particles have a particles 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 particles size less than or equal to the number D50 particle size. Thus, the number D50 particle size may be referred to as a median particle size. The number D90 particle size is defined such that 90% of the particles have a particles size less than or equal to the number D90 particle size. Thus, if there were 1 ,000 particles in the distribution and the particles were order by ascending particle size, one would expect the number D10 particle size to be roughly equal to the particle size of the 100th particle, the number D50 particle size to be roughly equal to the particle size of the 500th particle, and the number D90 particle size to be roughly equal to the particle size of the 900th particle.

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

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

A compromise has to be made when deciding the sizes of the particle. Larger thermally conductive particles may advantageously increase the thermal conductivity of the aerosolgenerating substrate more than smaller thermally conductive particles. However, larger thermal conductive particles may reduce the space available for aerosol-generating material in the substrate.

Optionally, the thermally conductive particles have a particle size distribution having a number D50 particle size, wherein the number 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 number D50 particle size, wherein the number D50 particle size is no more 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 particle size, wherein the number 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 number D90 particle size, wherein the number D90 particle size is no more 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 more 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 must be made in relation to the particle size distribution. A tighter particle size distribution, for example characterised by a smaller ratio between the D90 and D10 particle sizes, may advantageously provide a more uniform thermal conductivity throughout the aerosolgenerating substrate. This is because there will be less variation in particle size in different locations in the substrate. This may advantageously allow for more efficient usage of the aerosolgenerating material throughout the aerosol-generating substrate. However, a tighter particle size distribution may disadvantageously be more difficult and expensive to achieve. The inventors have found that the particle size distributions described above may provide an optimal 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 more 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 more 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 more than 1 ,000, 500, 200, 100, 50, 20, 10, 5, 2, 1 , 0.5, or 0.2 microns.

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

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 more 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 relation to the particle size distribution, and the inventors have found that the particle size distributions above may 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 1 ,000, 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 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 the aerosol-generating substrate. Particles greater than 300 microns may take up a rather large amount of space in the substrate which could be used for aerosol-generating material. Thus, 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 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 dimension, 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 substantially spherical particles may not affect the thermal conductivity of the substrate as much as the orientation of non-spherical particles. Thus, the use of more spherical particles may result in less variability between different substrates where the orientations of the particles is not controlled. In addition, substantially spherical particles may be more easy to characterise.

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-generating 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 wt % 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 wt % 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 50, 30 and 50, 40 and 50, 10 and 40, 20 and 40, 30 and 40, 10 and 30, 20 and 30, or 10 and 20 wt % 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, wt % of the thermally conductive particles.

A compromise must be made in relation to the weight percent of thermally conductive particles in the substrate. Increasing the weight percent of particles in the aerosol-generating substrate may advantageously increase the thermal conductivity of the substrate. However, increasing the weight percent of particles in the aerosol-generating substrate may also reduce the available space for one or more of the aerosol former, binder, and fibres, so could result in a substrate which forms less aerosol, or which has less tensile strength.

Optionally, the substrate comprises, on a dry weight basis, at least 10, 15, 20, 25, 30, 35, 40, 45, 50, or 55 wt % 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 wt % 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 wt % of the aerosol former. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 15 and 25 wt % 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 glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or tri-acetate; and aliphatic esters of mono-, di- or poly-carboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Optionally, the aerosol-generating substrate comprises one or both of glycerine and glycerol.

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

Optionally, the fibres are cellulose fibres. Advantageously, cellulose fibres are not overly costly and can increase the tensile strength of the substrate.

Optionally, each of the fibres 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 of the fibres 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 substrate comprises, on a dry weight basis, at least 4, 6, or 8 wt % of the binder. Optionally, the substrate comprises, on a dry weight basis, no more than 8, 6, or 4 wt % 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 wt % of the binder. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 2 and 10 wt % 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 derivitized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl cellulose; 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 carboxymethyl cellulose or hydroxypropyl cellulose or a gum such as guar gum.

Optionally, the thermally conductive particles are substantially homogeneously distributed throughout the aerosol-generating substrate. Optionally, the aerosol former is substantially homogeneously distributed throughout the aerosol-generating substrate. Optionally, the fibres are substantially homogeneously distributed throughout the aerosol-generating substrate. Optionally, the binder is substantially homogeneously distributed throughout the aerosol-generating substrate. Advantageously, a homogenous distribution of components of the substrate may result in the substrate have more spatially uniform properties. For example, substantially homogeneously distributed thermally conductive particles may result in the substrate having a substantially uniform thermal conductivity. As another example, substantially homogeneously distributed binder or fibres may result in the substrate having a 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 wt % nicotine. Optionally, the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2, or 1 wt % 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 wt % nicotine. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.5 and 4 wt % nicotine.

Optionally, the nicotine is substantially homogeneously distributed throughout the aerosolgenerating 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 wt % of the acid. Optionally, the substrate comprises, on a dry weight basis, no more than 5, 4, 3, 2 or 1 wt % 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 wt % of the acid. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 0.5 and 5 wt % 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 substantially homogeneously distributed throughout the aerosolgenerating 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 wt % of the at least one botanical. Optionally, the substrate comprises, on a dry weight basis, no more than 20, 15, 10, 5, 2 or 1 wt % of the at least one botanical. 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 wt % of the at least one botanical. It may be particularly preferable for the substrate to comprise, on a dry weight basis, between 1 and 15 wt % of the at least one botanical.

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

Optionally, the at least one botanical is substantially homogeneously distributed throughout the aerosol-generating substrate.

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

Optionally, the at least one flavourant is present as a coating, for example a coating on one or more other components of the aerosol-generating substrate. Alternatively, or in addition, the at least one flavourant is substantially homogeneously distributed throughout the aerosolgenerating substrate.

Optionally, the aerosol-generating 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, fragments of tobacco ribs, reconstituted tobacco, homogenised tobacco, extruded tobacco and expanded tobacco. Optionally, the at least one organic material is substantially homogeneously distributed throughout the aerosol-generating substrate.

The substrate may comprise, on a dry weight basis, less than 10, 5, 3, 2, or 1 wt % tobacco. Optionally, the aerosol-generating substrate is a tobacco-free aerosol-generating substrate. 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-generating substrate or in the rod of aerosol-generating substrate. That is, there may be no susceptor elements present in the aerosol-generating substrate or in the rod of aerosolgenerating substrate except for the thermally conductive or carbon particles.

Optionally, the aerosol-generating 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-generating 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-generating substrate has a density of between 600 and 1400, 800 and 1200, or 900 and 1100 kg/m³. Advantageously, reducing a density of the substrate may reduce transportation costs of the substrate.

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

Optionally, the aerosol-generating substrate comprises, or is in the form of, one or more of: cut-filler, powder particles, granules, pellets, shreds, spaghettis, strips, threads, ribbons, or sheets. Optionally, the aerosol-generating substrate comprises, or is in the form of, one or more sheets or strips.

Optionally, the aerosol-generating substrate comprises, or is in the form of, one or more sheets, for example gathered sheets. Optionally, the aerosol-generating substrate comprises, or is in the form of, a plurality of strips.

Optionally, the or each sheet or strip has a thickness of at least 5, 10, 20, 50, 100, 150, or 200 microns. Optionally, the or each sheet or strip has a thickness of no more than 2000, 1000, 500, 400, 300, or 250 microns. Optionally, the or each sheet or strip has a thickness of between 100 and 350, or 150 and 300 microns.

Optionally, the or each sheet or strip has a width of at least 100, 200, 500, or 1000 microns. Optionally, the or each sheet or strip has a width of no more than 2000, 1000, 500, 400, 300, 250, or 200 microns. Optionally, the or each sheet or strip has a width of between 100 and 2000, or 500 and 1000, or 600 and 1000 microns. Optionally, the or each sheet or strip has a length of at least 100, 200, 500, 1000, 2000, or 3000 microns. Optionally, the or each sheet or strip has a length of no more than 6000, 5000, 3000, 2000, 1000, 500, or 200 microns. Optionally, the or each sheet or strip has a length of between 100 and 6000, or 500 and 5000, or 1000 and 4000 microns.

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

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

Where the substrate comprises one or more gathered sheets, the or each gathered sheet may have a width of at least about 1 , 2, 5, 10, 25, 50, or 100 mm.

The aerosol-generating substrate comprising thermally conductive particles may be formed by a suitable method, such as a method comprising steps of: forming a slurry comprising the thermally conductive particles, the aerosol former, the fibres, and the binder; and casting and drying the slurry to form the aerosol-generating substrate or a precursor for forming into the aerosol-generating substrate.

Optionally, the slurry comprises water. Optionally, the slurry comprises between 20 and 90, 30 and 90, 40 and 90, 40 and 85, 50 and 80, 60 and 80, or 60 and 75 wt % 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 comprises forming a first mixture. The first mixture may comprise the aerosol former. The first mixture may comprise the fibres. The first mixture may comprise water. The first mixture may comprise the acid. The first mixture may comprise the nicotine. Forming the slurring may comprise forming a second mixture. The second mixture may comprise the thermally conductive particles. The second mixture may comprise the binder. Forming the slurry may comprise adding the second mixture to the first mixture to form a combined mixture.

Thus, forming the slurry may comprise: forming a first mixture comprising the aerosol former, the fibres, water, optionally, the acid, and optionally, the nicotine; forming a second mixture comprising the thermally conductive particles and the binder; and adding the second mixture to the first mixture to form a combined mixture.

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

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

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

Optionally, forming the first mixture comprises adding the fibres to the second pre-mixture.

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

Optionally, the method, for example the step of forming the slurry, 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 around 4 minutes.

Optionally, the method, for example the step of forming the slurry, comprises, after the first mixing, a second mixing. Optionally, the second mixing occurs under a second pressure which is less 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 slurry comprises casting the slurry onto a flat support, for example a steel flat support.

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

Optionally, drying the slurry comprises providing a flow of a gas such as air over or past the slurry. Optionally, the flow of gas is heated. Optionally, the flow of gas is heated to a temperature of between 100 and 160, or 120 and 140 degrees Celsius. Optionally, the flow of gas 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 wt %.

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

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 carbon layers (similar to graphite, for example) with spacing between the carbon layers greater than the spacing found between carbon layers in regular graphite. Expanded graphite may have carbon layers with elements or compounds intercalated into spaces between the carbon layers.

As used herein, the term “particle size” may refer to a single dimension and may be used to characterise the size of a given particle. The dimension may be the diameter of a spherical particle occupying the same volume as the given particle. All particle sizes and particle size distributions herein can be obtained using a standard laser diffraction technique. Particle sizes and particle size distributions as stated herein may be obtained using a commercially available sensor, for example a Sympatec HELOS laser diffraction sensor.

As used herein, where not otherwise specified, the term “density” may be used to refer to true density. Thus, where not 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 can vary greatly depending on how the powder or plurality of particles are handled). The measurement of true density can be done using a number of standard methods, these methods often being based on Archimedes’ principle. The most widely used method, when used to measure the true density of a powder, entails the powder being placed inside a container (a pycnometer) of known volume, and weighed. 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 as shown by the pycnometer, and the volume of liquid added (i.e. the volume of air displaced).

The wrapper circumscribing the rod of aerosol-generating substrate may be a paper wrapper or a non-paper wrapper. Suitable paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps. Suitable non-paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to sheets of homogenised tobacco materials. In certain preferred embodiments, the wrapper may be formed of a laminate material comprising a plurality of layers. Preferably, the wrapper is formed of an aluminium co-laminated sheet. The use of a co-laminated sheet comprising aluminium advantageously prevents combustion of the aerosolgenerating substrate in the event that the aerosol-generating substrate should be ignited, rather than heated in the intended manner.

In certain preferred embodiments of the present invention, an elongate susceptor element is arranged substantially longitudinally within the rod of aerosol-generating substrate and is in thermal contact with the aerosol-generating substrate.

As used herein, the term “susceptor element” refers to a material that can convert electromagnetic energy into heat. When located within a fluctuating electromagnetic field, eddy currents induced in the susceptor element cause heating of the susceptor element. As the elongate susceptor element is located in thermal contact with the aerosol-generating substrate, the aerosol-generating substrate is heated by the susceptor element.

The susceptor may be in direct contact with the aerosol-generating substrate. Inclusion of one or more carboxylic acids in the aerosol-generating substrate may advantageously reduce or prevent corrosion of the susceptor.

The susceptor may be located within an aerosol-generating rod comprising the aerosolgenerating substrate.

The susceptor may be located within the aerosol-generating substrate.

The aerosol-generating substrate may at least partially surround the susceptor.

The aerosol-generating substrate may be disposed on the susceptor. For example, where the aerosol-generating substrate is a solid aerosol-generating film, the susceptor may be at least partially coated with the solid aerosol-generating film.

The susceptor may be at least partially embedded in the aerosol-generating substrate. For example, where the aerosol-generating substrate is an aerosol-generating gel, the susceptor may be at least partially embedded in the aerosol-generating gel.

The susceptor may be an elongate susceptor.

When used for describing the susceptor element, the term “elongate” means that the susceptor element has a length dimension that is greater than its width dimension or its thickness dimension, for example greater than twice its width dimension or its thickness dimension.

The susceptor element is arranged substantially longitudinally within the rod. This means that the length dimension of the elongate susceptor element is arranged to be approximately parallel to the longitudinal direction of the rod, for example within plus or minus 10 degrees of parallel to the longitudinal direction of the rod. In preferred embodiments, the elongate susceptor element may be positioned in a radially central position within the rod, and extends along the longitudinal axis of the rod.

Preferably, the susceptor element extends all the way to a downstream end of the rod of aerosol-generating substrate. In some embodiments, the susceptor element may extend all the way to an upstream end of the rod of aerosol-generating substrate. In particularly preferred embodiments, the susceptor element has substantially the same length as the rod of aerosolgenerating substrate, and extends from the upstream end of the rod to the downstream end of the rod.

The susceptor element is preferably in the form of a pin, rod, strip or blade.

The susceptor element preferably has a length from about 6 millimetres to about 18 millimetres, for example from about 8 millimetres to about 16 millimetres, or from about 10 millimetres to about 14 millimetres. The susceptor may have a length that is substantially the same as the length of the solid aerosol-generating substrate or substantially the same as the length of an aerosol-generating rod comprising the solid aerosol-generating substrate.

The susceptor may extend along a longitudinal axis of the aerosol-generating article.

A ratio between the length of the susceptor element and the overall length of the aerosolgenerating article may be from about 0.20 to about 0.35.

Preferably, a ratio between the length of the susceptor element and the overall length of the aerosol-generating article is at least about 0.22, more preferably at least about 0.24, even more preferably at least about 0.26. A ratio between the length of the susceptor element and the overall length of the aerosol-generating article is preferably less than about 0.34, more preferably less than about 0.32, even more preferably less than about 0.30.

In some embodiments, a ratio between the length of the susceptor element and the overall length of the aerosol-generating article is preferably from about 0.22 to about 0.34, more preferably from about 0.24 to about 0.34, even more preferably from about 0.26 to about 0.34. In other embodiments, a ratio between the length of the susceptor element and the overall length of the aerosol-generating article is preferably from about 0.22 to about 0.32, more preferably from about 0.24 to about 0.32, even more preferably from about 0.26 to about 0.32. In further embodiments, a ratio between the length of the susceptor element and the overall length of the aerosol-generating article is preferably from about 0.22 to about 0.30, more preferably from about 0.24 to about 0.30, even more preferably from about 0.26 to about 0.30.

In a particularly preferred embodiment, a ratio between the length of the susceptor element and the overall length of the aerosol-generating article is about 0.27.

The susceptor may have any desired width. For example, the susceptor may have a width of between 2 millimetres and 8 millimetres, between 3 millimetres and 7 millimetres, or between 4 millimetres and 6 millimetres.

The susceptor may have any desired thickness. For example, the susceptor may have a thickness of between 30 micrometres and 90 micrometres, between 40 micrometres and 80 micrometres, or between 50 micrometres and 70 micrometres.

If the susceptor element has a constant cross-section, for example a circular cross-section, it has a preferable width or diameter from about 1 millimetre to about 5 millimetres.

If the susceptor element has the form of a strip or blade, the strip or blade preferably has a rectangular shape having a width of preferably from about 2 millimetres to about 8 millimetres, more preferably from about 3 millimetres to about 5 millimetres. By way of example, a susceptor element in the form of a strip of blade may have a width of about 4 millimetres.

If the susceptor element has the form of a strip or blade, the strip or blade preferably has a rectangular shape and a thickness from about 0.03 millimetres to about 0.15 millimetres, more preferably from about 0.05 millimetres to about 0.09 millimetres. By way of example, a susceptor element in the form of a strip of blade may have a thickness of about 0.07 millimetres.

In a preferred embodiment, the elongate susceptor element is in the form of a strip or blade, preferably has a rectangular shape, and has a thickness from about 55 micrometres to about 65 micrometres.

More preferably, the elongate susceptor element has a thickness from about 57 micrometres to about 63 micrometres. Even more preferably, the elongate susceptor element has a thickness from about 58 micrometres to about 62 micrometres. In a particularly preferred embodiment, the elongate susceptor element has a thickness of about 60 micrometres.

Preferably, the elongate susceptor element has a length which is the same or shorter than the length of the aerosol-generating substrate. Preferably, the elongate susceptor element has a same length as the aerosol-generating substrate.

The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the solid aerosol-generating substrate.

Preferably, the susceptor comprises a metal, an alloy or carbon.

Suitable susceptor materials include but are not limited to: carbon, carbon-based materials, graphene, graphite, expanded graphite, molybdenum, silicon carbide, stainless steels, niobium, aluminium, nickel, nickel-containing compounds, titanium, and composites of metallic materials. The susceptor may comprise or consist of a ferromagnetic material, for example a ferromagnetic alloy, ferritic iron, or a ferromagnetic steel or stainless steel. A suitable susceptor may comprise or consist of aluminium. 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 of ferromagnetic or paramagnetic materials. Preferred susceptor materials may comprise a metal, metal alloy or carbon.

The susceptor may be formed from 400 series stainless steels, for example grade 410 stainless steel, or grade 420 stainless steel, or grade 430 stainless steel. Different materials will dissipate different amounts of energy when positioned within electromagnetic fields having similar values of frequency and field strength.

The susceptor 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 may be inductively heated.

Thus, parameters of the susceptor element such as material type, length, width, and thickness may all be altered to provide a desired power dissipation within a known electromagnetic field. Preferred susceptor elements may be heated to a temperature in excess of 250 degrees Celsius.

Suitable susceptor elements may comprise a non-metallic core with a metal layer disposed on the non-metallic core, for example metallic tracks formed on a surface of a ceramic core. A susceptor element may have a protective external layer, for example a protective ceramic layer or protective glass layer encapsulating the susceptor element. The susceptor element may comprise a protective coating formed by a glass, a ceramic, or an inert metal, formed over a core of susceptor element material.

The susceptor element is arranged in thermal contact with the aerosol-generating substrate. Thus, when the susceptor element heats up the aerosol-generating substrate is heated up and an aerosol is formed. Preferably the susceptor element is arranged in direct physical contact with the aerosol-generating substrate, for example within the aerosol-generating substrate.

The susceptor element may be a multi-material susceptor element and may comprise a first susceptor element material and a second susceptor element material. The first susceptor element material is disposed in intimate physical contact with the second susceptor element material. The second susceptor element material preferably has a Curie temperature that is lower than 500 degrees Celsius. The first susceptor element material is preferably used primarily to heat the susceptor element when the susceptor element is placed in a fluctuating electromagnetic field. Any suitable material may be used. For example the first susceptor element material may be aluminium, or may be a ferrous material such as a stainless steel. The second susceptor element material is preferably used primarily to indicate when the susceptor element has reached a specific temperature, that temperature being the Curie temperature of the second susceptor element material. The Curie temperature of the second susceptor element material can be used to regulate the temperature of the entire susceptor element during operation. Thus, the Curie temperature of the second susceptor element material should be below the ignition point of the aerosol-generating substrate. Suitable materials for the second susceptor element material may include nickel and certain nickel alloys.

By providing a susceptor element having at least a first and a second susceptor element material, with either the second susceptor element material having a Curie temperature and the first susceptor element material not having a Curie temperature, or first and second susceptor element materials having first and second Curie temperatures distinct from one another, the heating of the aerosol-generating substrate and the temperature control of the heating may be separated. The first susceptor element material is preferably a magnetic material having a Curie temperature that is above 500 degrees Celsius. It is desirable from the point of view of heating efficiency that the Curie temperature of the first susceptor element material is above any maximum temperature that the susceptor element should be capable of being heated to. The second Curie temperature may preferably be selected to be lower than 400 degrees Celsius, preferably lower than 380 degrees Celsius, or lower than 360 degrees Celsius. It is preferable that the second susceptor element material is a magnetic material selected to have a second Curie temperature that is substantially the same as a desired maximum heating temperature. That is, it is preferable that the second Curie temperature is approximately the same as the temperature that the susceptor element should be heated to in order to generate an aerosol from the aerosol-generating substrate. The second Curie temperature may, for example, be within the range of 200 degrees Celsius to 400 degrees Celsius, or between 250 degrees Celsius and 360 degrees Celsius. The second Curie temperature of the second susceptor element material may, for example, be selected such that, upon being heated by a susceptor element that is at a temperature equal to the second Curie temperature, an overall average temperature of the aerosol-generating substrate does not exceed 240 degrees Celsius.

In some embodiments, the aerosol-generating section of the aerosol-generating articles of the present invention may comprise one or more upstream segments, at a location upstream of the rod of aerosol-generating substrate. In some embodiments, the aerosol-generating section may further comprise an upstream segment located upstream of and adjacent to the rod of aerosol-generating substrate. The upstream segment may abut the rod of aerosol-generating substrate. The upstream segment advantageously prevents direct physical contact with the upstream end of the aerosol-generating substrate. In particular, where the aerosol-generating substrate comprises a susceptor element, the upstream segment may prevent direct physical contact with the upstream end of the susceptor element. This helps to prevent the displacement or deformation of the susceptor element during handling or transport of the aerosol-generating article. This in turn helps to secure the form and position of the susceptor element. Furthermore, the presence of an upstream segment helps to prevent any loss of the substrate, which may be advantageous, for example, if the substrate contains particulate plant material.

The upstream segment may also provide an improved appearance to the upstream end of the aerosol-generating article. Furthermore, if desired, the upstream segment may be used to provide information on the aerosol-generating article, such as information on brand, flavour, content, or details of the aerosol-generating device that the article is intended to be used with.

The upstream segment may be a porous plug element. Preferably, a porous plug element does not alter the resistance to draw of the aerosol-generating article. Preferably, the upstream segment has a porosity of at least about 50 percent in the longitudinal direction of the aerosolgenerating article. More preferably, the upstream segment has a porosity of between about 50 percent and about 90 percent in the longitudinal direction. The porosity of the upstream segment in the longitudinal direction is defined by the ratio of the cross-sectional area of material forming the upstream segment and the internal cross-sectional area of the aerosol-generating article at the position of the upstream segment.

The upstream segment may be made of a porous material or may comprise a plurality of openings. This may, for example, be achieved through laser perforation. Preferably, the plurality of openings is distributed homogeneously over the cross-section of the upstream segment.

The porosity or permeability of the upstream segment may advantageously be varied in order to provide a desirable overall resistance to draw of the aerosol-generating article. Preferably, the RTD of the upstream segment is at least about 5 millimetres H2O. More preferably, the RTD of the upstream segment is at least about 10 millimetres H2O. Even more preferably, the RTD of the upstream segment is at least about 15 millimetres H2O. In particularly preferred embodiments, the RTD of the upstream segment is at least about 20 millimetres H2O.

The RTD of the upstream segment is preferably less than or equal to about 80 millimetres H2O. More preferably, the RTD of the upstream segment is less than or equal to about 60 millimetres H2O. Even more preferably, the RTD of the upstream segment is less than or equal to about 40 millimetres H2O.

In some embodiments, the RTD of the upstream segment is from about 5 millimetres H2O to about 80 millimetres H2O, preferably from about 10 millimetres H2O to about 80 millimetres H2O, more preferably from about 15 millimetres H2O to about 80 millimetres H2O, even more preferably from about 20 millimetres H2O to about 80 millimetres H2O. In other embodiments, the RTD of the upstream segment is from about 5 millimetres H2O to about 60 millimetres H2O, preferably from about 10 millimetres H2O to about 60 millimetres H2O, more preferably from about 15 millimetres H2O to about 60 millimetres H2O, even more preferably from about 20 millimetres H2O to about 60 millimetres H2O. In further embodiments, the RTD of the upstream segment is from about 5 millimetres H2O to about 40 millimetres H2O, preferably from about 10 millimetres H2O to about 40 millimetres H2O, more preferably from about 15 millimetres H2O to about 40 millimetres H2O, even more preferably from about 20 millimetres H2O to about 40 millimetres H2O.

In alternative embodiments, the upstream segment may be formed from a material that is impermeable to air. In such embodiments, the aerosol-generating article may be configured such that air flows into the rod of aerosol-generating substrate through suitable ventilation means provided in a wrapper.

The upstream segment may be made of any material suitable for use in an aerosolgenerating article. The upstream segment may, for example, be made of a same material as used for one of the other components of the aerosol-generating article, such as the mouthpiece, the cooling segment or the support segment. Suitable materials for forming the upstream segment include filter materials, ceramic, polymer material, cellulose acetate, cardboard, zeolite or aerosol-generating substrate. Preferably, the upstream segment is formed from a plug of cellulose acetate.

Preferably, the upstream segment is formed of a heat resistant material. For example, preferably the upstream segment is formed of a material that resists temperatures of up to 350 degrees Celsius. This ensures that the upstream segment is not adversely affected by the heating means for heating the aerosol-generating substrate.

Preferably, the upstream segment has a diameter that is approximately equal to the diameter of the aerosol-generating article. Preferably, the upstream segment has a length of between about 1 millimetre and about 10 millimetres, more preferably between about 3 millimetres and about 8 millimetres, more preferably between about 4 millimetres and about 6 millimetres. In a particularly preferred embodiment, the upstream segment has a length of about 5 millimetres. The length of the upstream segment can advantageously be varied in order to provide the desired total length of the aerosol-generating article. For example, where it is desired to reduce the length of one of the other components of the aerosol-generating article, the length of the upstream segment may be increased in order to maintain the same overall length of the article.

The upstream segment preferably has a substantially homogeneous structure. For example, the upstream segment may be substantially homogeneous in texture and appearance. The upstream segment may, for example, have a continuous, regular surface over its entire cross section. The upstream segment may, for example, have no recognisable symmetries.

The upstream segment is preferably circumscribed by a wrapper. The wrapper circumscribing the upstream segment is preferably a stiff plug wrap, for example, a plug wrap having a basis weight of at least about 80 grams per square metre (gsm), or at least about 100 gsm, or at least about 110 gsm. This provides structural rigidity to the upstream segment.

The aerosol-generating article according to the present invention may have a length from about 35 millimetres to about 100 millimetres.

Preferably, an overall length of an aerosol-generating article in accordance with the invention is at least about 38 millimetres. More preferably, an overall length of an aerosolgenerating article in accordance with the invention is at least about 40 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is at least about 42 millimetres.

An overall length of an aerosol-generating article in accordance with the invention is preferably less than or equal to 70 millimetres. More preferably, an overall length of an aerosolgenerating article in accordance with the invention is preferably less than or equal to 60 millimetres. Even more preferably, an overall length of an aerosol-generating article in accordance with the invention is preferably less than or equal to 50 millimetres.

In some embodiments, an overall length of the aerosol-generating article is preferably from about 38 millimetres to about 70 millimetres, more preferably from about 40 millimetres to about 70 millimetres, even more preferably from about 42 millimetres to about 70 millimetres. In other embodiments, an overall length of the aerosol-generating article is preferably from about 38 millimetres to about 60 millimetres, more preferably from about 40 millimetres to about 60 millimetres, even more preferably from about 42 millimetres to about 60 millimetres. In further embodiments, an overall length of the aerosol-generating article is preferably from about 38 millimetres to about 50 millimetres, more preferably from about 40 millimetres to about 50 millimetres, even more preferably from about 42 millimetres to about 50 millimetres. In an exemplary embodiment, an overall length of the aerosol-generating article is about 45 millimetres.

The aerosol-generating article preferably has an external diameter of at least 5 millimetres. Preferably, the aerosol-generating article has an external diameter of at least 6 millimetres. More preferably, the aerosol-generating article has an external diameter of at least 7 millimetres.

Preferably, the aerosol-generating article has an external diameter of less than or equal to about 12 millimetres. More preferably, the aerosol-generating article has an external diameter of less than or equal to about 10 millimetres. Even more preferably, the aerosol-generating article has an external diameter of less than or equal to about 8 millimetres.

In some embodiments, the aerosol-generating article has an external diameter from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 12 millimetres, more preferably from about 7 millimetres to about 12 millimetres. In other embodiments, the aerosol-generating article has an external diameter from about 5 millimetres to about 10 millimetres, preferably from about 6 millimetres to about 10 millimetres, more preferably from about 7 millimetres to about 10 millimetres. In further embodiments, the aerosol-generating article has an external diameter from about 5 millimetres to about 8 millimetres, preferably from about 6 millimetres to about 8 millimetres, more preferably from about 7 millimetres to about 8 millimetres.

In certain preferred embodiments of the invention, a diameter (DDE) of the aerosolgenerating article at the downstream end is (preferably) greater than a diameter (DUE) of the aerosol-generating article at the upstream end. In more detail, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosolgenerating article at the upstream end is (preferably) at least about 1.005.

Preferably, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is (preferably) at least about 1.01. More preferably, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is at least about 1 .02. Even more preferably, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is at least about 1 .05.

A ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is preferably less than or equal to about 1 .30. More preferably, a ratio (DDE/DUE) between the diameter of the aerosolgenerating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is less than or equal to about 1 .25. Even more preferably, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is less than or equal to about 1 .20. In particularly preferred embodiments, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is less than or equal to 1.15 or 1 .10.

In some preferred embodiments, a ratio (DDE/DUE) between the diameter of the aerosolgenerating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is from about 1.01 to 1.30, more preferably from 1.02 to 1 .30, even more preferably from 1.05 to 1.30.

In other embodiments, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is from about 1 .01 to 1 .25, more preferably from 1.02 to 1.25, even more preferably from 1 .05 to 1.25. In further embodiments, a ratio (DDE/DUE) between the diameter of the aerosol-generating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is from about 1 .01 to 1 .20, more preferably from 1.02 to 1.20, even more preferably from 1 .05 to 1.20. In yet further embodiments, a ratio (DDE/DUE) between the diameter of the aerosolgenerating article at the downstream end and the diameter of the aerosol-generating article at the upstream end is from about 1.01 to 1.15, more preferably from 1.02 to 1.15, even more preferably from 1.05 to 1.15.

By way of example, the external diameter of the article may be substantially constant over a distal portion of the article extending from the upstream end of the aerosol-generating article for at least about 5 millimetres or at least about 10 millimetres. As an alternative, the external diameter of the article may taper over a distal portion of the article extending from the upstream end for at least about 5 millimetres or at least about 10 millimetres.

In certain preferred embodiments of the present invention, the elements of the aerosolgenerating article, as described above, are arranged such that the centre of mass of the aerosolgenerating article is at least about 60 percent of the way along the length of the aerosol-generating article from the downstream end. More preferably, the elements of the aerosol-generating article are arranged such that the centre of mass of the aerosol-generating article is at least about 62 percent of the way along the length of the aerosol-generating article from the downstream end, more preferably at least about 65 percent of the way along the length of the aerosol-generating article from the downstream end.

Preferably, the centre of mass is no more than about 70 percent of the way along the length of the aerosol-generating article from the downstream end.

Providing an arrangement of elements that gives a centre of mass that is closer to the upstream end than the downstream end results in an aerosol-generating article having a weight imbalance, with a heavier upstream end. This weight imbalance may advantageously provide haptic feedback to the consumer to enable them to distinguish between the upstream and downstream ends so that the correct end can be inserted into an aerosol-generating device. This may be particularly beneficial where an upstream element is provided such that the upstream and downstream ends of the aerosol-generating article are visually similar to each other.

In embodiments of aerosol-generating articles in accordance with the invention, wherein both aerosol-cooling segment and support segment are present in the intermediate hollow section, these are preferably wrapped together in a combined wrapper. The combined wrapper circumscribes the aerosol-cooling segment and the support segment, but does not circumscribe segments further downstream, such as a mouthpiece filter segment.

In these embodiments, the aerosol-cooling segment and the support segment are combined prior to being circumscribed by the combined wrapper, before they are further combined with the mouthpiece filter segment.

From a manufacturing viewpoint, this is advantageous in that it enables shorter aerosolgenerating articles to be assembled.

In general, it may be difficult to handle individual elements that have a length smaller than their diameter. For example, for elements with a diameter of 7 millimetres, a length of about 7 millimetres represents a threshold value close to which it is preferable not to go. However, an aerosol-cooling element of 10 millimetres can be combined with a pair of support elements of 7 millimetres on each side (and potentially with other elements like the rod of aerosol-generating substrate, etc.) to provide a hollow segment of 24 millimetres, which is subsequently cut into two intermediate hollow sections of 12 millimetres.

In particularly preferred embodiments, the other components of the aerosol-generating article are individually circumscribed by their own wrapper. In other words, the upstream element, the rod of aerosol-generating substrate, the support segment, and the aerosol-cooling segment are all individually wrapped. The support segment and the aerosol-cooling segment are combined to form the intermediate hollow section. This is achieved by wrapping the support segment and the aerosol-cooling segment by means of a combined wrapper. The upstream segment, the rod of aerosol-generating substrate, and the intermediate hollow section are then combined together with an outer wrapper. Subsequently, they are combined with the mouthpiece section- which has a wrapper of its own - by means of tipping paper.

Preferably, at least one of the components of the aerosol-generating article is wrapped in a hydrophobic wrapper.

The term “hydrophobic” refers to a surface exhibiting water repelling properties. One useful way to determine this is to measure the water contact angle. The “water contact angle” is the angle, conventionally measured through the liquid, where a liquid/vapour interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid via the Young equation. Hydrophobicity or water contact angle may be determined by utilizing TAPPI T558 test method and the result is presented as an interfacial contact angle and reported in “degrees” and can range from near zero to near 180 degrees. In preferred embodiments, the hydrophobic wrapper is one including a paper layer having a water contact angle of about 30 degrees or greater, and preferably about 35 degrees or greater, or about 40 degrees or greater, or about 45 degrees or greater.

By way of example, the paper layer may comprise PVOH (polyvinyl alcohol) or silicon. The PVOH may be applied to the paper layer as a surface coating, or the the paper layer may comprise a surface treatment comprising PVOH or silicon.

In a particularly preferred embodiment, an aerosol-generating article in accordance with the present invention comprises, in linear sequential arrangement, an upstream segment, a rod of aerosol-generating substrate located immediately downstream of the upstream segment, a support segment located immediately downstream of the rod of aerosol-generating substrate, an aerosol-cooling segment located immediately downstream of the support segment, a mouthpiece filter segment located immediately downstream of the aerosol-cooling segment, and an outer wrapper circumscribing the upstream segment, the rod of aerosol-generating substrate, the support segment, the aerosol-cooling segment and the mouthpiece filter segment.

In more detail, the rod of aerosol-generating substrate may abut the upstream segment. The support segment may abut the rod of aerosol-generating substrate. The aerosol-cooling segment may abut the support segment. The mouthpiece segment may abut the aerosol-cooling segment.

The aerosol-generating article has a substantially cylindrical shape and an outer diameter of about 7.25 millimetres.

The upstream segment has a length of about 5 millimetres, the rod of aerosol-generating substrate has a length of about 12 millimetres, the support segment has a length of about 8 millimetres, the aerosol-cooling segment has a length of about 13 millimetres, the mouthpiece filter segment has a length of about 7 millimetres. Thus, an overall length of the aerosolgenerating article is about 45 millimetres.

The upstream segment is in the form of a plug of cellulose acetate wrapped in stiff plug wrap.

The aerosol-generating article comprises an elongate susceptor element arranged substantially longitudinally within the rod of aerosol-generating substrate and is in thermal contact with the aerosol-generating substrate. The susceptor element is in the form of a strip or blade, has a length substantially equal to the length of the rod of aerosol-generating substrate and a thickness of about 60 micrometres.

The support segment is in the form of a hollow cellulose acetate tube and has an internal diameter of about 1.9 millimetres. Thus, a thickness of a peripheral wall of the support element is about 2.675 millimetres. The aerosol-cooling segment is in the form of a finer hollow cellulose acetate tube and has an internal diameter of about 3.25 millimetres. Thus, a thickness of a peripheral wall of the aerosol-cooling element is about 2 millimetres.

The mouthpiece is in the form of a low-density cellulose acetate filter segment.

The rod of aerosol-generating substrate comprises at least one of the types of aerosolgenerating substrate described above, such as homogenised tobacco, a gel formulation or a homogenised plant material comprising particles of a plant other than tobacco, an aerosolgenerating film or thermally conductive particles.

In the following, the invention will be further described with reference to accompanying Figures 1 and 2, which shows a schematic side sectional view of aerosol-generating articles in accordance with the invention.

The aerosol-generating article 10 shown in Figure 1 comprises an aerosol-generating section 52, an intermediate hollow section 50, and a mouthpiece section 64. The aerosolgenerating section comprises a rod 12 of aerosol-generating substrate and an upstream segment 16 at a location upstream of the rod 12 of aerosol-generating substrate.

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

The aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or mouth end 20. The aerosol-generating article comprises a rod 12 of aerosolgenerating substrate and a downstream section 14 at a location downstream of the rod 12 of aerosol-generating substrate. The downstream section 14 comprises a support segment 22 located immediately downstream of the rod 12 of aerosol-generating substrate, the support segment 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1 , the upstream end 30 of the support segment 22 abuts the downstream end of the rod 12 of aerosolgenerating substrate. In addition, the downstream section 14 comprises an aerosol-cooling segment 24 located immediately downstream of the support segment 22, the aerosol-cooling segment 24 being in longitudinal alignment with the rod 12 and the support segment 22. In the embodiment of Figure 1 , the upstream end 38 of the aerosol-cooling segment 24 abuts the downstream end of the support segment 22.

As will become apparent from the following description, the support segment 22 and the aerosol-cooling segment 24 together define an intermediate hollow section 50 of the aerosolgenerating article 10. As a whole, the intermediate hollow section 50 does not substantially contribute to the overall RTD of the aerosol-generating article. An RTD of the intermediate hollow section 50 as a whole is substantially 0 millimetres H2O.

The support segment 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an internal cavity 28 that extends all the way from an upstream end 30 of the first hollow tubular segment to an downstream end 32 of the first hollow tubular segment 20. The internal cavity 28 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 28. The first hollow tubular segment 26 - and, as a consequence, the support segment 22 - does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the first hollow tubular segment 26 (which is essentially the RTD of the support segment 22) is substantially 0 millimetres H₂O.

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

The aerosol-cooling segment 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an internal cavity 36 that extends all the way from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The internal cavity 36 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 36. The second hollow tubular segment 34 - and, as a consequence, the aerosol-cooling segment 24 - does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the second hollow tubular segment 34 (which is essentially the RTD of the aerosol-cooling element 24) is substantially 0 millimetres H₂O.

The second hollow tubular segment 34 has a length of about 13 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (DSTS) of about 3.25 millimetres. Thus, a thickness of a peripheral wall of the second hollow tubular segment 34 is about 2 millimetres. Thus, a ratio between the internal diameter (DFTS) of the first hollow tubular segment 26 and the internal diameter (DSTS) of the second hollow tubular segment 34 is about 0.75.

The aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. In more detail, the ventilation zone is provided at about 2 millimetres from the upstream end of the second hollow tubular segment 34. A ventilation level of the aerosol-generating article 10 is about 25 percent.

In the embodiment of Figure 1 , the downstream section 14 further comprises a mouthpiece filter segment 42 at a location downstream of the intermediate hollow section 50. In more detail, the mouthpiece filter segment 42 is positioned immediately downstream of the aerosol-cooling element 24. As shown in the drawing of Figure 1 , an upstream end of the mouthpiece filter segment 42 abuts the downstream end 40 of the aerosol-cooling element 18.

The mouthpiece filter segment 42 is provided in the form of a cylindrical plug of low-density cellulose acetate.

The mouthpiece filter segment 42 has a length of about 7 millimetres and an external diameter of about 7.25 millimetres. The RTD of the mouthpiece filter segment 42 is about 7 millimetres H2O. The ratio of the length of the mouthpiece filter segment 42 to the length of the intermediate hollow section 50 is approximately 0.33.

The rod 12 comprises an aerosol-generating substrate of one of the types described above.

The rod 12 of aerosol-generating substrate has an external diameter of about 7.25 millimetres and a length of about 12 millimetres.

The aerosol-generating article 10 further comprises an elongate susceptor element 44 within the rod 12 of aerosol-generating substrate. In more detail, the susceptor element 44 is arranged substantially longitudinally within the aerosol-generating substrate, such as to be approximately parallel to the longitudinal direction of the rod 12. As shown in the drawing of Figure 1 , the susceptor element 44 is positioned in a radially central position within the rod and extends effectively along the longitudinal axis of the rod 12.

The susceptor element 44 extends all the way from an upstream end to a downstream end of the rod 12. In effect, the susceptor element 44 has substantially the same length as the rod 12 of aerosol-generating substrate.

In the embodiment of Figure 1 , the susceptor element 44 is provided in the form of a strip and has a length of about 12 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres. The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of aerosol-generating substrate, the upstream element 46 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1 , the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of aerosol-generating substrate. This advantageously prevents the susceptor element 44 from being dislodged. Further, this ensures that the consumer cannot accidentally contact the heated susceptor element 44 after use.

The upstream segment 46 is provided in the form of a cylindrical plug of cellulose acetate circumscribed by a stiff wrapper. The upstream segment 46 has a length of about 5 millimetres. The RTD of the upstream element 46 is about 30 millimetres H2O.

Figure 2 shows an aerosol-generating article 100 which is a variant of the aerosolgenerating article 10 described above. The aerosol-generating article 100 differs from aerosolgenerating article 10 by the provision of an additional aerosol-cooling segment 58, which comprises a third hollow tubular segment 54. Thus the intermediate hollow section 50 comprises the support segment 22, the aerosol-cooling segment 24, and the additional aerosol-cooling segment 58. The third hollow tubular segment 54 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The third hollow tubular segment 54 defines an internal cavity 56. The third hollow tubular segment 54 abuts the upstream end 62 of the mouthpiece filter 42. The internal cavity 56 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 56. The third hollow tubular segment 54 - and, as a consequence, the additional aerosol-cooling segment 58 - does not substantially contribute to the overall RTD of the aerosol-generating article 100. In more detail, the RTD of the third hollow tubular segment 54 (which is essentially the RTD of the aerosol-cooling element 58) is substantially 0 millimetres H₂O.

In the embodiment of article 100, the second hollow tubular segment 34 has a length of about 8 millimetres and the third hollow tubular segment 54 has a length of about 5 millimetres.

Claims

1. An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article extending from a downstream end to an upstream end and comprising: an aerosol-generating section comprising a rod of aerosol-generating substrate; a mouthpiece section comprising a mouthpiece filter segment formed of a fibrous filtration material, the mouthpiece section having a length L1 extending between the upstream end of the mouthpiece filter segment and the downstream end of the aerosol-generating article; and an intermediate hollow section having a length L2 extending between the aerosolgenerating section and the mouthpiece section, the intermediate hollow section defining a longitudinal cavity providing an unrestricted flow channel from the aerosol-generating section to the mouthpiece section, the intermediate hollow section comprising: an aerosol-cooling segment downstream of the aerosol-generating section; and a support segment between the aerosol-cooling segment and the aerosolgenerating section, wherein the length of the mouthpiece section (L1) is at least 0.10 times and less than 0.34 times the length of the intermediate hollow section (L2).

2. An aerosol-generating article according to claim 1 , wherein the length of the mouthpiece section is at least 0.20 times the length of the intermediate hollow section.

3. An aerosol-generating article according to claim 1 or 2, wherein the length of the mouthpiece section is at least 0.30 times the length of the intermediate hollow section.

4. An aerosol-generating article according to any one of claims 1 to 3, wherein the mouthpiece section comprises a mouthpiece filter segment having a length that is at least 0.10 times and less than 0.34 times the length of the intermediate hollow section (L2).

5. An aerosol-generating article according to any preceding claim, wherein the length of the mouthpiece section is about 1 mm to about 10 mm, preferably about 5 mm to about 9 mm, most preferably about 7 mm.

6. An aerosol-generating article according to any preceding claim, wherein the mouthpiece section comprises a mouthpiece filter segment having a length that is about 1 mm to about 10 mm, preferably about 5 mm to about 9 mm, most preferably about 7 mm.

7. An aerosol-generating article according to any preceding claim, wherein the resistance to draw (RTD) of the mouthpiece section is less than about 10 mm H2O, most preferably about 7 mm H2O.

8. An aerosol-generating article according to any preceding claim, wherein the aerosolcooling segment comprises a hollow tubular segment defining a longitudinal cavity providing an unrestricted flow channel, and further comprises a ventilation zone at a position along the hollow tubular segment.

9. An aerosol-generating article according to any preceding claim, wherein the aerosolgenerating substrate is a solid aerosol-generating substrate comprising nicotine, one or more cellulose based agents, one or more aerosol formers, and one or more carboxylic acids, wherein the solid aerosol-generating substrate has a total cellulose based agent content of at least 35 percent by weight, a total aerosol former content of greater than or equal to 45 percent by weight, and a total carboxylic acid content of at least 0.5 percent by weight.

10. An aerosol-generating article according to claim 9, wherein the solid aerosol-generating substrate comprises one or more carboxylic acids selected from acetic acid, adipic acid, benzoic acid, citric acid, fumaric acid, maleic acid, malic acid, myristic acid, oxalic acid, salicylic acid, stearic acid, succinic acid, undecanoic acid and C1-C10 saturated alkyl mono-carboxylic acids.

11. An aerosol-generating article according to claim 9 or 10, wherein the solid aerosolgenerating substrate comprises fumaric acid.

12. An aerosol-generating article according to any one of claims 9 to 11 , wherein the solid aerosol-generating substrate further comprises one or more carboxylic acids selected from lactic acid and levulinic acid.

13. An aerosol-generating article according to any one of claims 9 to 12, wherein the solid aerosol-generating substrate has a total carboxylic acid content of between 1 percent and 6 percent by weight.

14. An aerosol-generating article according to any one of claims 9 to 13, wherein the solid aerosol-generating substrate has a total cellulose based agent content of between 35 percent by weight and 50 percent by weight.

15. An aerosol-generating article according to any one of claims 9 to 14, wherein the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents selected from carboxymethyl cellulose and hydroxypropylmethyl cellulose.