Aerosol-generating article comprising an aerosol-generating substrate surrounded by a high-porosity annular portion

Abstract

The aerosol-generating article (10) for generating an inhalable aerosol when heated comprises an aerosol-generating rod (12) extending from an upstream end to a downstream end, and a downstream section (14) provided downstream of the aerosol-generating rod (12) and abutting the downstream end of the aerosol-generating rod (12). The aerosol-generating rod (12) comprises a substantially cylindrical core portion (20) having a longitudinal axis, and an annular portion (24) surrounding the core portion (20) and extending coaxially therewith. The annular portion is air permeable such that the upstream end of the annular portion is in fluid communication with the downstream section (14). The core portion (20) comprises an aerosol-generating substrate and has a cross-sectional porosity of 0.10 to 0.45. The cross-sectional porosity of the annular portion (24) is at least 120 percent of the cross-sectional porosity of the core portion (20).

Description

[Technical field]

[0001] The present invention relates to an aerosol-generating article comprising an aerosol-generating substrate and adapted to generate an inhalable aerosol upon heating. [Background technology]

[0002] Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than burned, are known in the art.Typically, in such heated smoking articles, aerosol is generated by transferring heat from a heat source to a physically separated aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source.During the use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in the air drawn through the aerosol-generating article.As the released compounds cool, they condense to form an aerosol.

[0003] Numerous prior art documents disclose aerosol generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol generating devices, in which the aerosol is generated by heat transfer from one or more electric heater elements of the aerosol generating device to an aerosol-generating substrate of the heated aerosol-generating article. For example, an electrically heated aerosol generating device has been proposed, which includes an internal heater blade adapted to be inserted into the aerosol-generating substrate. As an alternative, WO2015 / 176898 proposes an inductively heated aerosol-generating article, which includes an aerosol-generating substrate and a susceptor disposed within the aerosol-generating substrate. A further alternative is described in WO2020 / 115151, which discloses an aerosol-generating article used in combination with an external heating system comprising one or more heating elements disposed around the outer surface of the aerosol-generating article. For example, the external heating element may be provided in the form of a flexible heating foil on a dielectric substrate, such as polyimide. Summary of the Invention [Problem to be solved by the invention]

[0004] Aerosol-generating articles in which the tobacco-containing substrate is heated rather than combusted present several challenges not faced by conventional smoking articles. First, the tobacco-containing substrate is typically heated to a significantly lower temperature compared to the temperature reached by the combustion front of a conventional cigarette. This can affect the nicotine release from the tobacco-containing substrate and the nicotine delivery to the consumer. Furthermore, it can be difficult to uniformly heat the entire tobacco-containing substrate provided in the article.

[0005] In aerosol generating systems where heat is supplied internally, such as by a heater element inserted into the rod of the aerosol-generating substrate, it may be difficult to efficiently transfer the heat supplied by the heater element all the way to the periphery of the rod, whereas in aerosol generating systems where heat is supplied externally, such as by inserting the aerosol-generating article into a cavity of a heating device comprising one or more heater elements disposed about the side walls of the cavity, it may be difficult to efficiently transfer the heat supplied by the heater element all the way to the core of the rod.

[0006] Difficulties in efficiently transferring heat may result in portions of the rod of aerosol-generating substrate not being able to reach a sufficient temperature to facilitate emission of the aerosol species, which may undesirably result in less than ideal utilization of the aerosol-generating substrate provided within the rod, as those portions of the rod of aerosol-generating substrate may not contribute substantially to the overall aerosol delivery of the aerosol-generating article.

[0007] Difficulties in efficiently transferring heat can also lead to portions of the rod of aerosol-generating substrate that actually reach a temperature sufficient to promote emission of aerosol species, but over only a small portion of the use cycle of the aerosol-generating article, where the temperature profile during use may differ from the intended temperature profile, and so the aerosol-generating substrate may be undesirably underutilized.

[0008] The problems discussed above can be further complicated by the fact that an aerosol-generating article can be heated in any commercially available aerosol-generating device, as long as it is compatible with the size, i.e., diameter, of the aerosol-generating article, regardless of whether the particular model of aerosol-generating article and aerosol-generating device were designed to be used together. One such potential mismatch of the aerosol-generating article and device, possibly combined with non-ideal airflow mechanisms through the system during use, can lead to the aerosol-generating substrate being exposed to a temperature profile that is not optimized. This can adversely affect aerosol delivery and temperature, and generally change the conditions of use of the system relative to those intended.

[0009] Generally, therefore, a need is felt for an aerosol-generating article that can be adapted to address one or more of the problems discussed above. Furthermore, it would be desirable to provide an aerosol-generating article that is easy to manufacture, making the entire production chain more sustainable and cost-effective. It would therefore be desirable to provide a new and improved aerosol-generating article that is configured to meet at least one of the above needs. Furthermore, it would also be desirable to provide one such aerosol-generating article that can be manufactured efficiently and quickly. [Brief description of the drawings]

[0010] [Figure 1] 1 shows a schematic cross-sectional side view of an aerosol-generating article according to one embodiment of the present invention. [Diagram 2] 4 shows a schematic cross-sectional view of the aerosol-generating article of FIG. 1 taken along line IV-IV. [Diagram 3] FIG. 3 shows a schematic cross-sectional side view of an aerosol generating system according to one embodiment of the invention comprising the aerosol generating article of FIGS. 1 and 2 and an aerosol generating device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present disclosure relates to an aerosol-generating article for generating an inhalable aerosol upon heating. The aerosol-generating article may comprise an aerosol-generating rod extending from an upstream end to a downstream end. The aerosol-generating article may further comprise a downstream section provided downstream of the aerosol-generating rod. The downstream section may abut the downstream end of the aerosol-generating rod. The aerosol-generating rod may comprise a substantially cylindrical core portion having a longitudinal axis and an annular portion surrounding the core portion and extending coaxially with the core portion. The annular portion may be air permeable. The annular portion may be in direct fluid communication with the downstream section. The core portion may comprise an aerosol-generating substrate. The core portion may have a cross-sectional porosity of 0.10 to 0.45. The cross-sectional porosity of the annular portion may be at least 120 percent of the cross-sectional porosity of the core portion.

[0012] The present disclosure further relates to an aerosol generating system comprising the above-mentioned aerosol generating article and an aerosol generating device including a heating chamber opening at a proximal end for at least partially receiving an aerosol generating rod to heat an aerosol-generating substrate. The aerosol generating device may include an opening at a distal end for allowing airflow into the heating chamber along a longitudinal axis of the heating chamber. The diameter of the opening may be smaller than the inner diameter of the annular portion.

[0013] According to the present invention, there is provided an aerosol-generating rod extending from an upstream end to a downstream end, and a downstream section provided downstream of the aerosol-generating rod and abutting the downstream end of the aerosol-generating rod. The aerosol-generating rod may include a substantially cylindrical core portion having a longitudinal axis, and an annular portion surrounding the core portion and extending coaxially therewith. The annular portion is air permeable such that the upstream end of the annular portion is in fluid communication with the downstream section. The core portion includes an aerosol-generating substrate and has a cross-sectional porosity of 0.10 to 0.45, the cross-sectional porosity of the annular portion being at least 120 percent of the cross-sectional porosity of the core portion.

[0014] According to the present invention, there is provided an aerosol generating system comprising an aerosol generating article as described above and an aerosol generating device comprising a heating chamber at a proximal end for at least partially receiving the aerosol generating rod and for heating the aerosol generating substrate, the aerosol generating device including an opening at a distal end for allowing airflow into the heating chamber along a longitudinal axis of the heating chamber, the diameter of the opening being smaller than the inner diameter of the annular portion.

[0015] The aerosol-generating article according to the invention thus provides a novel arrangement of a section of the aerosol-generating article configured to generate an aerosol upon heating. More particularly, there is provided a substantially cylindrical core section containing the aerosol-generating substrate and surrounded by an air-permeable annular section having a relatively high cross-sectional porosity. The annular section is sized such that direct fluid communication can be established between the annular section and the downstream section.

[0016] The annular portion is air permeable and has a significantly higher cross-sectional porosity compared to the core portion, and the resistance to draw (RTD) of the annular portion is substantially lower than that of the core portion. Thus, when the aerosol-generating article is not paired with an aerosol-generating device, air drawn into the aerosol-generating article by a consumer may flow mainly, if not entirely, through the annular portion and around the core portion. Thus, the aerosol-generating substrate in the core portion may be substantially bypassed by such air flow. Thus, the functionality of the aerosol-generating article may be substantially limited when a consumer inhales through the aerosol-generating article when the aerosol-generating article is not paired with an aerosol-generating device.

[0017] This is advantageous in that misuse of the aerosol-generating article is generally prevented: for example, attempts by some consumers to use the aerosol-generating article as a conventional combustible smoking article may generally fail because the airflow into the core portion at the upstream end of the aerosol-generating article is insufficient to sustain combustion.

[0018] Furthermore, since the aerosol-generating substrate is concentrated in the core of the aerosol-generating rod, a homogenous supply of heat to all of the aerosol-generating substrate during use may be advantageously promoted in systems in which heat is supplied to the aerosol-generating article from within, as described in more detail below. The supply of heat to the annular portion surrounding the core portion is of no importance, since it is not intended to contribute to aerosol generation. The fact that the air-permeable annular portion may not heat up significantly in systems in which heat is supplied to the aerosol-generating article from within may further be beneficial in certain embodiments, since the annular portion may function to some extent as an insulating sleeve.

[0019] Furthermore, the core portion and the annular portion may be dimensioned such that the aerosol-generating article is only compatible for use with an aerosol-generating device having a particular design, such that when the aerosol-generating article is coupled to the aerosol-generating device, the upstream end of the annular portion may be blocked while allowing airflow to the core portion In contrast, if the aerosol-generating article is coupled to the wrong aerosol-generating device, the upstream end of the core portion may be at least partially blocked while allowing airflow to the annular portion, thereby effectively making use of the aerosol-generating article impossible.

[0020] For example, in a system according to the invention, an opening is provided at the distal end of the aerosol generating device to allow air to enter the heated chamber within which the aerosol generating article is received. By ensuring that the diameter of the opening is smaller than the inner diameter of the annular portion, it is advantageously possible to ensure perfect compatibility of use between the aerosol generating article and the aerosol generating device.

[0021] This has the advantage that use of the aerosol-generating article only with a corresponding dedicated aerosol-generating device ensures that the aerosol-generating substrate is fully functional and is subjected to a predetermined heating profile specifically designed for that aerosol-generating substrate, whereas an improper match of the aerosol-generating article with an aerosol-generating device other than the aerosol-generating device for which the aerosol-generating article is intended may generally be ineffective. Thus, mismatching of the aerosol-generating article with the aerosol-generating device is prevented, while at the same time ensuring that aerosol delivery and other parameters may be optimized when the aerosol-generating article is correctly paired with the intended aerosol-generating device.

[0022] As briefly described above, according to 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 rod extending from an upstream end to a downstream end. A core portion of the aerosol-generating rod comprises an aerosol-generating substrate.

[0023] The term "aerosol-generating article" is used herein to mean an article in which an aerosol-generating substrate is heated to generate an inhalable aerosol for delivery to a consumer. As used herein, the term "aerosol-generating substrate" means a substrate capable of releasing a volatile compound upon heating to generate an aerosol.

[0024] A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. Localized heat provided by the flame and oxygen in the air drawn through the cigarette ignites the end of the cigarette and the resulting combustion produces inhalable smoke. In contrast, in heated aerosol-generating articles, the aerosol is generated by heating a flavor-generating substrate (such as tobacco). Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which the aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separated aerosol-forming material. For example, the aerosol-generating article according to the present invention finds particular application in aerosol-generating systems comprising an electrically heated aerosol generator having an internal heater blade adapted to be inserted into a rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example in EP0822670.

[0025] As used herein, the term "aerosol-generating device" refers to a device that includes a heater element that interacts with an aerosol-generating substrate of an aerosol-generating article to generate an aerosol.

[0026] As used herein in connection with the present invention, the term "rod" is used to denote a generally cylindrical element of substantially circular, oval or elliptical cross section.

[0027] The term "longitudinal" as used herein refers to a direction corresponding to a major longitudinal axis of the aerosol-generating article extending between the upstream and downstream ends of the aerosol-generating article. The terms "upstream" and "downstream" as used herein describe the relative positions of an element (or portion of an element) of the aerosol-generating article with respect to the direction in which aerosol is transported through the aerosol-generating article during use.

[0028] During use, air is drawn longitudinally through the aerosol-generating article. The term "transverse" refers to a direction perpendicular to the longitudinal axis. Any reference to a "cross section" of an aerosol-generating article or a component of an aerosol-generating article refers to a transverse cross section, unless otherwise specified.

[0029] The term "length" refers to the dimension of a component of an aerosol-generating article in a longitudinal direction. For example, it may be used to refer to the dimension of a rod or elongated tubular element in a longitudinal direction.

[0030] The aerosol-generating article further comprises a downstream section at a location downstream of the aerosol-generating rod. As will become apparent from the following description of different embodiments of the aerosol-generating article of the present invention, the downstream section may comprise one or more downstream elements.

[0031] In some embodiments, the downstream section may include a hollow section between the mouth end of the aerosol-generating article and the aerosol-generating rod. The hollow section may comprise a hollow tubular element.

[0032] As used herein, the term "hollow tubular segment" or "hollow tubular element" refers to a generally elongated element that defines a cavity or airflow passage along its longitudinal axis. In particular, the term "tubular" is used hereinafter with reference to an element or segment that has a substantially cylindrical cross-section and defines at least one airflow conduit that establishes uninterrupted fluid communication between an upstream end of the tubular element or segment and a downstream end of the tubular element or segment. However, it will be appreciated that alternative shapes (e.g., alternative cross-sectional shapes) of the tubular element or segment may be possible.

[0033] In the context of the present invention, a hollow tubular segment or hollow tubular element provides an unrestricted flow path. This means that the hollow tubular segment or hollow tubular element provides a negligible level of resistance to withdrawal (RTD). The term "negligible level of RTD" is used to describe an RTD of less than 1 mmH2O per 10 millimeters of length of a hollow tubular segment or hollow tubular element, preferably less than 0.4 mmH2O per 10 millimeters of length of a hollow tubular segment or hollow tubular element, more preferably less than 0.1 mmH2O per 10 millimeters of length of a hollow tubular segment or hollow tubular element.

[0034] Thus, the flow channels should not include any components that would impede the longitudinal air flow. Preferably, the flow channels are substantially empty.

[0035] As used herein, a "hollow tubular segment" or "hollow tubular element" may also be referred to as a "hollow tube" or "hollow tube segment."

[0036] In some embodiments, the aerosol-generating article may include a ventilation zone at a location along the downstream section. More particularly, the aerosol-generating article may, in certain embodiments, include a ventilation zone at a location along the hollow tubular element. In this manner, fluid communication is established between a flow channel defined internally by the hollow tubular element and the external environment.

[0037] In the aerosol-generating article according to the invention, the aerosol-generating rod may have a length of at least 5 mm. Preferably, the aerosol-generating rod has a length of at least 10 mm. More preferably, the aerosol-generating rod has a length of at least 12 mm. Even more preferably, the aerosol-generating rod has a length of at least 15 mm.

[0038] Preferably, the length of the aerosol-generating rod is equal to or less than 45 mm. More preferably, the length of the aerosol-generating rod is equal to or less than 40 mm. Even more preferably, the length of the aerosol-generating rod is equal to or less than 40 mm.

[0039] In a preferred embodiment, the length of the aerosol-generating rod is 35 millimeters or less. More preferably, the length of the aerosol-generating rod is 30 millimeters or less. Even more preferably, the length of the aerosol-generating rod is 25 millimeters or less. In a particularly preferred embodiment, the length of the aerosol-generating rod is 22 millimeters or less.

[0040] In some embodiments, the length of the aerosol-generating rod is between 10 mm and 45 mm, preferably between 10 mm and 40 mm, more preferably between 10 mm and 35 mm, even more preferably between 10 mm and 30 mm. In particularly preferred embodiments, the length of the aerosol-generating rod is between 10 mm and 25 mm, preferably between 10 mm and 22 mm.

[0041] In other embodiments, the length of the aerosol-generating rod is between 12 mm and 45 mm, preferably between 12 mm and 40 mm, more preferably between 12 mm and 35 mm, even more preferably between 12 mm and 30 mm.In a particularly preferred embodiment, the length of the aerosol-generating rod is between 12 mm and 25 mm, preferably between 12 mm and 22 mm.

[0042] In a further embodiment, the length of the aerosol-generating rod is between 15 mm and 45 mm, preferably between 15 mm and 40 mm, more preferably between 15 mm and 35 mm, even more preferably between 15 mm and 30 mm.In a particularly preferred embodiment, the length of the aerosol-generating rod is between 15 mm and 25 mm, preferably between 15 mm and 22 mm.

[0043] As briefly described above, in an aerosol-generating article according to the invention, the aerosol-generating rod comprises a core portion having a longitudinal axis. The core portion preferably has a substantially uniform cross-section along the length of the aerosol-generating rod. It is particularly preferred that the core portion has a substantially circular cross-section, such that the core portion may be described as substantially cylindrical.

[0044] The core portion includes an aerosol-generating substrate and has a cross-sectional porosity of 0.10 to 0.45.

[0045] As used herein, the term "porosity" refers to the proportion of void space within an air-permeable or porous body. More specifically, the term "porosity" is used herein with reference to the "cross-sectional porosity" of one such body, i.e., the proportion of void space in the cross-sectional area of ​​the air-permeable or porous body, for example, the cross-sectional area of ​​the cylindrical core portion of the aerosol-generating rod of an aerosol-generating article according to the invention. The cross-sectional porosity is the areal percentage of void space in the transverse cross-sectional area of ​​the cylindrical core portion. The transverse cross-sectional area of ​​the cylindrical core portion is the area of ​​the cylindrical core portion in a plane perpendicular to the longitudinal axis of the aerosol-generating rod.

[0046] As used herein, the term "value of porosity distribution" or "value of cross-sectional porosity distribution" refers to the standard deviation of the porosity values ​​determined locally within each of a plurality of identically sized sub-areas across the cross-sectional area of ​​the air-permeable or porous body. The porosity within a sub-area is also referred to as the "local porosity" and the value of the cross-sectional porosity distribution is the standard deviation of the local porosity values ​​across the cross-sectional area of ​​the air-permeable or porous body.

[0047] A subarea refers to an area smaller than the cross-sectional area of ​​the body. A plurality of equally sized subareas cover the entire cross-sectional area of ​​the body. Each subarea preferably overlaps at least one adjacent subarea, preferably two or more adjacent subareas. Each subarea preferably overlaps at least one adjacent subarea by 10 to 95 percent. Each subarea is preferably less than 20 percent of the total cross-sectional area, for example less than 15 percent of the total cross-sectional area, preferably less than 10 percent of the total cross-sectional area.

[0048] In the case of a cylindrical body, such as the core portion of an aerosol-generating rod in an aerosol-generating article according to the invention, the transverse cross-sectional area will be substantially circular. Each sub-area is preferably rectangular or square. Preferably, the sub-areas overlap at least 50 percent of the transverse cross-sectional area before being included in the calculation of the porosity distribution, and particularly preferably overlap at least 70 percent or at least 80 percent or at least 90 percent of the transverse cross-sectional area before being included in the calculation of the porosity distribution.

[0049] As described in more detail below, in certain preferred embodiments in which the aerosol-generating substrate comprises a sheet of aerosol-forming material assembled to form a core portion, the cross-sectional porosity of the core portion is a function of the diameter of the core portion and of the width and thickness of the sheet of aerosol-forming material. In such embodiments, the cross-sectional porosity of the core portion may be calculated using the formula: [Formula 1] TIFF2024539441000002.tif2668 formula, P cross = cross-sectional porosity D cp = Core diameter W sheet = Width of the sheets that come together to form the core T sheet = Thickness of the sheets that assemble to form the core

[0050] The cross-sectional porosity distribution value refers to a measure of the variation in local porosity for different sub-areas of the transverse cross-sectional area of ​​the body.

[0051] Therefore, the cross-sectional porosity distribution value is a quantitative measure of the distribution of porosity over a cross-sectional area of ​​the article. The local porosity of each sub-area may be calculated using the following formula: [Formula 2] TIFF2024539441000003.tif1546 formula, P local = Sectional porosity of the sub-area A local = Area of ​​the subarea Asheet = Area of ​​tobacco material in a sub-area

[0052] The cross-sectional porosity distribution value may be considered as a measure of the uniformity of the porosity of a body, such as a cylindrical body. For example, if the standard deviation of the local porosity is low, the voids in the cylindrical body are likely to be uniformly distributed and of similar size across the cross-sectional area of ​​the cylindrical body. However, if the standard deviation is high, the voids are not uniformly distributed across the cross-sectional area of ​​the cylindrical body, with some sections of the cylindrical body having high porosity and some parts having low porosity. For a given cross-sectional porosity, a high cross-sectional porosity distribution value may indicate that the cylindrical body has a small number of relatively large through-channels, and a low cross-sectional porosity distribution value may indicate that the cylindrical body has a large number of relatively small through-channels.

[0053] The cross-sectional porosity distribution value may be determined from local porosity values ​​calculated for multiple sub-areas covering a transverse cross section of a single body. The cross-sectional porosity distribution value associated with any individual rod may be compared to the value of another individual body. Alternatively, the cross-sectional porosity distribution value may be calculated from local porosity values ​​derived from a set or batch of multiple different bodies of approximately the same cross-sectional area and approximately the same cross-sectional porosity, e.g., cylindrical bodies. The cross-sectional porosity distribution value from a batch of bodies may be used to assess the quality of porosity between one batch of bodies, such as cylindrical bodies, and another batch of cylindrical bodies.

[0054] Advantageously, the values ​​of cross-sectional porosity and cross-sectional porosity distribution can be determined using digital image processing processes. An image of a cross-section of the core portion can be acquired and a threshold applied to distinguish pixels representing the aerosol-forming substrate from pixels representing voids. The porosity of the entire cross-section can then be easily obtained.

[0055] The cross-sectional porosity distribution value is preferably determined by a method including the steps of obtaining a digital image of the transverse cross-sectional area of ​​the rod, determining the areal percentage of porosity present within each of a plurality of equally sized subareas of the transverse area to thereby obtain a porosity value for each of the plurality of equally sized subareas, and calculating the standard deviation of the porosity values ​​for each of the plurality of equally sized subareas, each subarea overlapping with at least one adjacent subarea by between 10 percent and 95 percent, preferably between 75 percent and 85 percent, preferably about 80 percent.

[0056] The core portion is substantially cylindrical and has an average diameter, for example, an average diameter of about 4.5 mm. Each of the subareas is preferably rectangular or square with a length of 1 / 4 to 1 / 8 of the diameter of the core portion, preferably 1 / 6 or 1 / 7 of the diameter of the core portion. Thus, if the diameter of the core portion is about 4.5 mm, the subareas may be square with sides about 0.75 mm long.

[0057] The porosity value of any individual sub-area is preferably only included in the calculations for assessing the porosity distribution if 90 percent or more of that sub-area is within the transverse cross-sectional area of ​​the core portion.

[0058] Preferably, the digital image of the cross-sectional area is made up of a plurality of pixels, each pixel constituting the cross-sectional area being contained within at least one of the plurality of sub-areas.

[0059] Further details regarding the measurement of cross-sectional porosity and cross-sectional porosity distribution in porous or air-permeable bodies can be found in International Patent Application Publication No. WO2016 / 023965 filed in the name of the applicant.

[0060] In an aerosol-generating article according to the invention, the core portion preferably has a cross-sectional porosity of at least 0.15. More preferably, in an aerosol-generating article according to the invention, the core portion has a cross-sectional porosity of at least 0.20.

[0061] Preferably, the core portion has a cross-sectional porosity of 0.40 or less. More preferably, the core portion has a cross-sectional porosity of 0.35 or less. Even more preferably, the core portion has a cross-sectional porosity of 0.25 or less.

[0062] In some embodiments, the core portion has a cross-sectional porosity of 0.15 to 0.40, preferably 0.15 to 0.35, and more preferably 0.15 to 0.25, while in other embodiments, the core portion has a cross-sectional porosity of 0.20 to 0.40, preferably 0.20 to 0.35, and more preferably 0.20 to 0.25.

[0063] The core portion may have a cross-sectional porosity distribution value, calculated using the method described above, of at least 0.04, with each subarea being a square having a side length of 1 / 7 of the diameter of the core portion and each subarea overlapping with at least one other subarea by about 80 percent.Preferably, the core portion may have a cross-sectional porosity distribution value, calculated using the method described above, of at least 0.10, with each subarea being a square having a side length of 1 / 7 of the diameter of the core portion and each subarea overlapping with at least one other subarea by about 80 percent.

[0064] The core portion may have a cross-sectional porosity distribution value calculated using the method described above of 0.22 or less, where each subarea is a square having a side length of 1 / 7 of the core portion diameter and where each subarea overlaps with at least one other subarea by about 80 percent. Preferably, the core portion may have a cross-sectional porosity distribution value calculated using the method described above of 0.20 or less, where each subarea is a square having a side length of 1 / 7 of the core portion diameter and where each subarea overlaps with at least one other subarea by about 80 percent. More preferably, the core portion may have a cross-sectional porosity distribution value calculated using the method described above of 0.15 or less, where each subarea is a square having a side length of 1 / 7 of the core portion diameter and where each subarea overlaps with at least one other subarea by about 80 percent.

[0065] In some embodiments, the core portion may have a cross-sectional porosity distribution value of 0.04 to 0.22, preferably 0.04 to 0.20, more preferably 0.04 to 0.15. In other embodiments, the core portion may have a cross-sectional porosity distribution value of 0.10 to 0.22, preferably 0.10 to 0.20, more preferably 0.10 to 0.15. In the aerosol-generating article according to the invention, the outer diameter of the cylindrical core portion may be at least 1 millimeter. Preferably, the outer diameter of the core portion is at least 3 millimeters. More preferably, the outer diameter of the core portion is at least 3.5 millimeters. Preferably, the outer diameter of the core portion is less than 8 millimeters. More preferably, the outer diameter of the core portion is less than 7 millimeters. Even more preferably, the outer diameter of the core portion is less than 5.75 millimeters.

[0066] In some embodiments, the outer diameter of the core portion is between 3 mm and 8 mm, preferably between 3 mm and 7 mm, and more preferably between 3 mm and 5.75 mm. In other embodiments, the outer diameter of the core portion is between 3.5 mm and 8 mm, preferably between 3.5 mm and 7 mm, and more preferably between 3.5 mm and 5.75 mm.

[0067] Preferably, the density of the aerosol-generating substrate is at least about 150 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is at least about 175 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is at least about 200 mg per cubic centimeter. Even more preferably, the density of the aerosol-generating substrate is at least about 250 mg per cubic centimeter. Even more preferably, the density of the aerosol-generating substrate is at least about 300, 400, 500 mg per cubic centimeter. Preferably, the density of the aerosol-generating substrate is not more than about 1500 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is not more than about 1000 mg per cubic centimeter. More preferably, the density of the aerosol-generating substrate is not more than about 800 mg per cubic centimeter. Even more preferably, the density of the aerosol-generating substrate is not more than about 700 mg per cubic centimeter.

[0068] For example, the density of the aerosol-generating substrate is preferably from about 150 mg per cubic centimeter to about 1500 mg per cubic centimeter, preferably from about 175 mg per cubic centimeter to about 450 mg per cubic centimeter, more preferably from about 200 mg per cubic centimeter to about 400 mg per cubic centimeter, and even more preferably from 250 mg per cubic centimeter to 350 mg per cubic centimeter. In a particularly preferred embodiment of the present invention, the density of the aerosol-generating substrate is about 300 mg per cubic centimeter.

[0069] In certain preferred embodiments, the aerosol-generating substrate of the core portion comprises cut tobacco material (e.g., tobacco cut filler) and has a density of from about 150 mg per cubic centimeter to about 500 mg per cubic centimeter, preferably from about 175 mg per cubic centimeter to about 450 mg per cubic centimeter, more preferably from about 200 mg per cubic centimeter to about 400 mg per cubic centimeter, more preferably from about 250 mg per cubic centimeter to about 350 mg per cubic centimeter, and most preferably about 300 mg per cubic centimeter.

[0070] The aerosol-generating substrate may be a solid aerosol-generating substrate. The aerosol-generating substrate preferably comprises an aerosol former. The aerosol former may be any suitable known compound or mixture of compounds that promotes the formation of a dense and stable aerosol during use. The aerosol former may promote the aerosol to be substantially resistant to thermal decomposition at temperatures typically encountered during use of the aerosol-generating article. Suitable aerosol formers are, for example, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, propylene glycol, glycerin, etc.), esters of polyhydric alcohols (e.g., glycerol mono-, di-, or triacetate, etc.), aliphatic esters of mono-, di-, or polycarboxylic acids (e.g., dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.), and combinations thereof.

[0071] The aerosol former preferably comprises one or more of glycerin and propylene glycol. The aerosol former may consist of glycerin, or propylene glycol, or a combination of glycerin and propylene glycol.

[0072] The aerosol-generating substrate preferably comprises at least 5 weight percent of aerosol formers based on the dry weight of the aerosol-generating substrate, more preferably from 10 weight percent to 22 weight percent based on the dry weight of the cut aerosol-generating substrate, more preferably the amount of aerosol formers is from 12 weight percent to 19 weight percent based on the dry weight of the aerosol-generating substrate, most preferably the amount of aerosol formers is from 13 weight percent to 16 weight percent based on the dry weight of the aerosol-generating substrate.

[0073] In certain preferred embodiments of the present invention, the aerosol-generating substrate comprises cut tobacco material. For example, the cut tobacco material may be in the form of cut filler, as described in more detail below. Alternatively, the cut tobacco material may be in the form of a cut sheet of homogenized tobacco material. Suitable homogenized tobacco materials for use in the present invention are described below.

[0074] In the context of this specification, the term "cut filler" is used to describe a blend of finely chopped plant material, such as tobacco plant material, specifically including one or more of leaf blades, processed stems and veins, and homogenized plant material.

[0075] Cut filler may also include other cuts, filler tobacco, or casings.

[0076] Preferably, the cut filler comprises at least 25 percent of the plant leaf lamina, more preferably at least 50 percent of the plant leaf lamina, even more preferably at least 75 percent of the plant leaf lamina, and most preferably at least 90 percent of the plant leaf lamina. Preferably, the plant material is one of tobacco, mint, tea, and clove. Most preferably, the plant material is tobacco. However, as discussed in more detail below, the present invention is equally applicable to other plant materials that have the ability, upon application of heat, to release a substance that can then form an aerosol.

[0077] Preferably, the cut filler comprises tobacco plant material including the blades of one or more of bright tobacco, dark tobacco, aromatic tobacco, and filler tobacco. For purposes of the present invention, the term "tobacco" describes any plant of the genus Nicotiana.

[0078] Bright tobacco is a tobacco having generally large, light-colored leaves. Throughout this specification, the term "bright tobacco" is used for flue-cured tobacco. Examples of bright tobacco include Chinese flue-cured tobacco, flue-cured Brazilian tobacco, American flue-cured tobacco (such as Virginia tobacco), Indian flue-cured tobacco, Tanzanian flue-cured tobacco, or other African flue-cured tobacco. Bright tobacco is characterized by a high sugar-to-nitrogen ratio. From a sensory perspective, bright tobacco is a tobacco type with a spicy, lively sensation after curing. In the context of the present invention, bright tobacco is a tobacco having a reducing sugar content of about 2.5 percent to about 20 percent based on dry weight of the leaf and a total ammonia content of less than about 0.12 percent based on dry weight of the leaf. Reducing sugars include, for example, glucose or fructose. Total ammonia includes, for example, ammonia and ammonia salts.

[0079] Dark tobacco is tobacco that generally has large dark leaves. Throughout this specification, the term "dark tobacco" is used for air-cured tobacco. Additionally, dark tobacco may be fermented. Tobaccos that are primarily used for chewing tobacco, snuff, cigar tobacco, and pipe blends are also included in this category. Typically, these dark tobaccos are air-cured and sometimes fermented. From a sensory perspective, dark tobacco is a tobacco type with a smoky, dark cigar-type sensation after curing. Dark tobacco is characterized by a low sugar-to-nitrogen ratio. Examples of dark tobacco are Burley Malawi or other African Burley, dark-cured Brazilian Galpao, San-cured or air-cured Indonesian Kasturi. According to the present invention, dark tobacco is tobacco that has a reducing sugar content of less than about 5 percent based on dry weight of the leaf and a total ammonia content of about 0.5 percent or less based on dry weight of the leaf.

[0080] Aromatic tobacco is tobacco that often has small, light-colored leaves. Throughout this specification, the term "aromatic tobacco" is used for other tobaccos that have a high aromatic content, such as a high content of essential oils. From a sensory perspective, aromatic tobacco is a tobacco type that, after curing, has a spicy and aromatic sensation. Examples of aromatic tobacco are Greek Orient, Oriental Turkish, Semi-Orient tobacco, but also fire-cured, US Burley such as Perique, Rustic, US Burley, or Maryland. Filler tobacco is not a specific tobacco type, but includes tobacco types that are primarily used to complement other tobacco types used in the blend and do not bring a specific characteristic aroma direction to the final product. Examples of filler tobacco are the stems, midribs, or petioles of other tobacco types. A specific example can be the flue-cured stems of the lower petioles of Brazilian flue-cured petioles.

[0081] The cut filler suitable for use in the present invention may generally be similar to the cut filler used in conventional smoking articles. The cut width of the cut filler is preferably 0.3 mm to 2.0 mm, more preferably the cut width of the cut filler is 0.5 mm to 1.2 mm, and most preferably the cut width of the cut filler is 0.6 mm to 0.9 mm. The cut width may play a role in the distribution of heat inside the rod of the aerosol-generating substrate. The cut width may also play a role in the drawing resistance of the core portion. Furthermore, the cut width may affect the overall density and cross-sectional porosity of the core portion as a whole.

[0082] The strand length of the cut filler is somewhat random, since the length of the strand depends on the overall size of the object from which it is cut. Nevertheless, longer strands can be cut by conditioning the material before cutting, for example by controlling the moisture content and overall fineness of the material. Preferably, the strands have a length of about 10 millimeters to about 40 millimeters, after which the strands are aligned to form the rod of the aerosol-generating substrate. Obviously, if the strands are disposed in the rod of the aerosol-generating substrate at a longitudinal extension of the section that is less than 40 millimeters, the final core portion of the aerosol-generating substrate may contain strands that are on average shorter than the initial strand length. The strand length of the cut filler is preferably such that about 20 percent to 60 percent of the strands extend along the entire length of the rod of the aerosol-generating substrate. This prevents the strands from easily detaching from the rod of the aerosol-generating substrate.

[0083] In a preferred embodiment, the weight of the cut filler is 80 milligrams to 400 milligrams, preferably 150 milligrams to 250 milligrams, more preferably 170 milligrams to 220 milligrams. This amount of cut filler can typically be enough material for the formation of an aerosol. Additionally, in light of the aforementioned constraints on diameter and size, this allows for a balanced density of the core portion comprising the aerosol-generating substrate between energy uptake, drawing resistance, and fluid passage in the rod of the aerosol-generating substrate when the aerosol-generating substrate comprises plant material.

[0084] The cut filler is preferably soaked with the aerosol former. Soaking of the cut filler can be by spraying or other suitable application methods. The aerosol former can be added to the blend during preparation of the cut filler. For example, the aerosol former can be applied to the blend in a direct conditioning casing cylinder (DCCC). Conventional machinery can be used to add the aerosol former to the cut filler. The aerosol former can be any suitable known compound or mixture of compounds that promotes the formation of a dense and stable aerosol during use. The aerosol former can promote the aerosol to be substantially resistant to thermal decomposition at temperatures typically applied during use of the aerosol-generating article. Suitable aerosol formers are, for example, polyhydric alcohols (such as, for example, triethylene glycol, 1,3-butanediol, propylene glycol, and glycerin), esters of polyhydric alcohols (such as, for example, glycerol monoacetate, diacetate, or triacetate), aliphatic esters of mono-, di-, or polycarboxylic acids (such as, for example, dimethyl dodecanedioate and dimethyl tetradecanedioate), and combinations thereof.

[0085] The aerosol former preferably comprises one or more of glycerin and propylene glycol. The aerosol former may consist of glycerin, or propylene glycol, or a combination of glycerin and propylene glycol.

[0086] Preferably, the amount of the aerosol former is at least 5 weight percent based on the dry weight of the cut filler, preferably 10 weight percent to 22 weight percent based on the dry weight of the cut filler, more preferably the amount of the aerosol former is 12 weight percent to 19 weight percent based on the dry weight of the cut filler, for example, the amount of the aerosol former is 13 weight percent to 16 weight percent based on the dry weight of the cut filler. When the aerosol former is added to the cut filler in the above-mentioned amount, the cut filler can become relatively sticky. This advantageously helps to hold the cut filler in place within the article, since the particles of the cut filler tend to adhere not only to the surrounding cut filler particles, but also to surrounding surfaces (e.g., the inner surface of the wrapper surrounding the cut filler).

[0087] In some embodiments, the amount of aerosol former has a target value of about 13 weight percent based on the dry weight of the cut filler. The most effective amount of aerosol former also depends on the cut filler and whether the cut filler includes plant lamina or homogenized plant material. For example, the type of cut filler, among other factors, determines the extent to which the aerosol former can facilitate the release of material from the cut filler.

[0088] For these reasons, a core portion containing cut filler as described above as an aerosol-generating substrate has the ability to efficiently generate a sufficient amount of aerosol at a relatively low temperature. A temperature of 150°C to 200°C in a heating chamber may be sufficient for one such cut filler to generate a sufficient amount of aerosol, while a temperature of about 250°C is typically employed in an aerosol-generating device using tobacco cast leaf sheets.

[0089] A further advantage associated with operating at lower temperatures is that the need for cooling the aerosol is reduced: since lower temperatures are typically used, simpler cooling mechanisms may be sufficient, which in turn allows for the use of simpler and less complex structures for the aerosol-generating article.

[0090] In another preferred embodiment, the aerosol-generating substrate comprises homogenized plant material, preferably homogenized tobacco material.

[0091] As used herein, the term "homogenized plant material" encompasses any plant material formed by agglomeration of plant particles. For example, a sheet or web of homogenized tobacco material for an aerosol-generating substrate of the present invention may be formed by agglomerating particles of tobacco material obtained by grinding, crushing, or comminuting plant material and, optionally, one or more of tobacco lamina and tobacco stems. Homogenized plant material may be produced by casting, extrusion, a papermaking process, or any other suitable process known in the art.

[0092] The homogenized plant material can be provided in any suitable form.

[0093] In some embodiments, the homogenized plant material may be in the form of one or more sheets. The term "sheet" as used herein with respect to the present invention describes a laminar element having a width and length that is significantly greater than its thickness.

[0094] The homogenized plant material may be in the form of a plurality of pellets or granules.

[0095] The homogenized plant material may be in the form of multiple strands, strips, or pieces. As used herein, the term "strand" describes an elongated element of material having a length substantially greater than its width and thickness. The term "strand" should be considered to encompass strips, pieces, and any other homogenized plant material having a similar morphology. Strands of homogenized plant material may be formed from a sheet of homogenized plant material, for example, by cutting or shredding, or by other methods, such as extrusion methods.

[0096] In some embodiments, the strands may be formed in situ within the aerosol-generating substrate as a result of splitting or breaking apart of a sheet of homogenized plant material during formation of the aerosol-generating substrate, e.g., as a result of crimping. The strands of homogenized plant material within the aerosol-generating substrate may be separated from one another. Alternatively, each strand of homogenized plant material within the aerosol-generating substrate may be at least partially connected to adjacent strands along the length of the strand. For example, adjacent strands may be connected by one or more fibers. This may occur, for example, when strands are formed due to splitting of a sheet of homogenized plant material during manufacture of the aerosol-generating substrate, as described above.

[0097] As mentioned above, when the homogenized plant material is in the form of one or more sheets, the sheets may be produced by a casting process. Alternatively, the sheets of homogenized plant material may be produced by a papermaking process.

[0098] One or more sheets as described herein may each individually have a thickness of from 100 micrometers to 600 micrometers, preferably from 150 micrometers to 300 micrometers, and most preferably from 200 micrometers to 250 micrometers. Individual thickness refers to the thickness of an individual sheet, and combined thickness refers to the total thickness of all sheets that make up the aerosol-generating substrate. For example, when the aerosol-generating substrate is formed from two individual sheets, the combined thickness is the thickness of the two individual sheets, or the sum of the measured thicknesses of the two sheets, which are stacked in the aerosol-generating substrate.

[0099] One or more sheets as described herein may each individually have a basis weight of from about 100 grams per square meter to about 600 grams per square meter.

[0100] One or more sheets as described herein may each individually have a density of from about 0.3 grams per cubic centimeter to about 1.3 grams per cubic centimeter, preferably from about 0.7 grams per cubic centimeter to about 1.0 grams per cubic centimeter.

[0101] In embodiments of the invention in which the aerosol-generating substrate comprises one or more sheets of homogenized plant material, the sheets are preferably in the form of an assembly of one or more sheets, the term "assembly" as used herein meaning that the sheet of homogenized plant material is coiled, folded or otherwise compressed or contracted in a direction substantially transverse to the cylindrical axis of the plug or rod.

[0102] One or more sheets of homogenized plant material may be assembled transversely to their longitudinal axes and surrounded by a wrapper to form a continuous rod or plug.

[0103] The sheet or sheets of homogenized plant material may advantageously be crimped or similarly treated. As used herein, the term "crimped" means a sheet having a plurality of substantially parallel ridges or corrugations. The sheet or sheets of homogenized plant material may be embossed, debossed, perforated, or otherwise deformed to provide texture to one or both sides of the sheet.

[0104] Preferably, each sheet of homogenized plant material may be crimped to have a plurality of ridges or corrugations substantially parallel to the cylindrical axis of the plug. This process advantageously facilitates assembling the crimped sheets of homogenized plant material to form a plug. Preferably, one or more sheets of homogenized plant material may be assembled. Of course, the crimped sheets of homogenized plant material may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that are at an acute or obtuse angle to the cylindrical axis of the plug. The sheet may be crimped to an extent that the integrity of the sheet is disturbed at the plurality of parallel ridges or corrugations, causing separation of the material and resulting in the formation of pieces, strands or strips of homogenized plant material.

[0105] Alternatively, one or more sheets of homogenized plant material may be cut into strands as mentioned above. In such an embodiment, the aerosol-generating substrate comprises a plurality of strands of homogenized plant material. The strands may be used to form the core portion as a plug. Typically, such strands have a width of about 5 millimeters, or about 4 millimeters, or about 3 millimeters, or about 2 millimeters, or less. The length of the strands may be greater than about 5 millimeters, about 5 millimeters to about 15 millimeters, about 8 millimeters to about 12 millimeters, or about 12 millimeters. It is preferred that the strands have substantially the same length as each other.

[0106] The homogenized plant material may comprise up to about 95 percent by weight plant particles on a dry weight basis, preferably up to about 90 percent by weight plant particles, more preferably up to about 80 percent by weight plant particles, more preferably up to about 70 percent by weight plant particles, more preferably up to about 60 percent by weight plant particles, and more preferably up to about 50 percent by weight plant particles on a dry weight basis.

[0107] For example, the homogenized plant material can contain, on a dry weight basis, from about 2.5 weight percent to about 95 weight percent plant particles, or from about 5 weight percent to about 90 weight percent plant particles, or from about 10 weight percent to about 80 weight percent plant particles, or from about 15 weight percent to about 70 weight percent plant particles, or from about 20 weight percent to about 60 weight percent plant particles, or from about 30 weight percent to about 50 weight percent plant particles.

[0108] In certain embodiments of the invention, the homogenized plant material is a homogenized tobacco material comprising tobacco particles. The sheets of homogenized tobacco material used in such embodiments of the invention may have a tobacco content of at least about 40 weight percent on a dry weight basis, more preferably at least about 50 weight percent on a dry weight basis, more preferably at least about 70 weight percent on a dry weight basis, and most preferably at least about 90 weight percent on a dry weight basis.

[0109] In the context of the present invention, the term "tobacco particles" refers to particles of any plant member of the Nicotiana species. The term "tobacco particles" encompasses ground or powdered tobacco lamina, ground or powdered tobacco stems, tobacco dust, tobacco fines, and other particulate tobacco by-products formed during tobacco processing, handling, and shipping. In a preferred embodiment, the tobacco particles are substantially entirely derived from tobacco lamina. In contrast, isolated nicotine and nicotine salts, although compounds derived from tobacco, are not considered tobacco particles for purposes of the present invention and are not included in the percentage of particulate plant material.

[0110] The homogenized plant material may further include one or more aerosol formers. Upon volatilization, the aerosol formers can carry other vaporized compounds released from the aerosol-generating substrate upon heating, such as nicotine and flavorants in the aerosol. Aerosol formers suitable for inclusion in the homogenized 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 tetradecanedioate).

[0111] The homogenized plant material may have an aerosol former content of about 5 weight percent to about 30 weight percent on a dry weight basis (such as about 10 weight percent to about 25 weight percent on a dry weight basis, or about 15 weight percent to about 20 weight percent on a dry weight basis). The aerosol former may act as a humectant in the homogenized plant material.

[0112] The core portion may include a core wrapper surrounding the aerosol-generating substrate. The core wrapper is thus interposed between the aerosol-generating substrate and the annular portion, with the outer surface of the core wrapper effectively defining the outer surface of the core portion. In certain embodiments in which the annular portion radially abuts the core portion, the outer surface of the core wrapper abuts the inner surface of the annular portion, such that the core wrapper effectively defines the interface between the core portion and the annular portion.

[0113] The aerosol-generating rod may then generally include a rod wrapper surrounding the annular portion, such that the outer surface of the rod wrapper defines the outer surface of the aerosol-generating rod.

[0114] The core wrapper surrounding the aerosol-generating substrate can be a paper wrapper or a non-paper wrapper.Similarly, the rod wrapper surrounding the annular portion can be a paper wrapper or a non-paper wrapper.

[0115] The core wrapper may have an air permeability of less than 1000 Coresta units. In certain preferred embodiments, the core wrapper has an air permeability of 100 Coresta units or less. More preferably, the core wrapper has an air permeability of 80 Coresta units or less. Even more preferably, the core wrapper has an air permeability of 60 Coresta units or less.

[0116] The core wrapper may have an air permeability of at least 5 Coresta units. Preferably, the core wrapper has an air permeability of at least 10 Coresta units. More preferably, the core wrapper has an air permeability of at least 20 Coresta units.

[0117] In certain embodiments, the core wrapper has an air permeability of from 5 Coresta units to 100 Coresta units, preferably from 5 Coresta units to 80 Coresta units, more preferably from 5 Coresta units to 60 Coresta units. In other embodiments, the core wrapper has an air permeability of from 10 Coresta units to 100 Coresta units, preferably from 10 Coresta units to 80 Coresta units, more preferably from 10 Coresta units to 60 Coresta units. In further embodiments, the core wrapper has an air permeability of from 20 Coresta units to 100 Coresta units, preferably from 20 Coresta units to 80 Coresta units, more preferably from 20 Coresta units to 60 Coresta units.

[0118] By providing a core wrapper having an air permeability within the above preferred ranges, radial air flow may be impeded or substantially prevented from crossing the core wrapper such that air flow from the core portion into the annular portion and vice versa is substantially prevented.

[0119] This may advantageously enhance the technical advantages discussed above in connection with the present invention because when the aerosol-generating article is not paired with an aerosol-generating device or when the aerosol-generating article is paired with the wrong aerosol-generating device, the low-permeability core wrapper substantially prevents lateral airflow from the annular portion from entering into the core portion, so that substantially all air drawn into the annular portion flows in the longitudinal axis through the annular portion from one end to the other. Thus, the low-permeability core wrapper works in synergy with the substantial difference in cross-sectional porosity and relative arrangement of the core portion and the annular portion.

[0120] Suitable paper wrappers for use in certain embodiments of the present invention are known in the art and include, but are not limited to, cigarette paper and filter plug wrap. Suitable non-paper wrappers for use in certain embodiments of the present invention are known in the art and include, but are not limited to, sheets of homogenized tobacco material. The characteristics of suitable paper and non-paper wrappers are described in more detail below. The paper and non-paper wrappers described below may be used as a core wrapper, as a rod wrapper, or both.

[0121] The paper wrapper may have a basis weight of at least 15 gsm, preferably at least 20 gsm. The paper wrapper may have a basis weight of 35 gsm or less, preferably 30 gsm or less. The paper wrapper may have a basis weight of 15 gsm to 35 gsm, preferably 20 gsm to 30 gsm. In a preferred embodiment, the paper wrapper may have a basis weight of 25 gsm. The paper wrapper may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, more preferably at least 35 micrometers. The paper wrapper may have a thickness of about 55 micrometers or less, preferably about 50 micrometers or less, more preferably about 45 micrometers or less. The paper wrapper may have a thickness of 25 micrometers to 55 micrometers, preferably 30 micrometers to 50 micrometers, more preferably 35 micrometers to 45 micrometers. In a preferred embodiment, the paper wrapper may have a thickness of 40 microns.

[0122] In certain preferred embodiments, the wrapper may be formed from a laminate material comprising multiple layers. Preferably, the wrapper is formed from an aluminum co-laminate sheet. The use of an aluminum-containing co-laminate sheet advantageously prevents combustion of the aerosol-generating substrate if the aerosol-generating substrate is to be ignited rather than heated in the intended manner.

[0123] The paper layer of the co-laminate sheet may have a basis weight of at least 35 gsm, preferably at least 40 gsm. The paper layer of the co-laminate sheet may have a basis weight of 55 gsm or less, preferably 50 gsm or less. The paper layer of the co-laminate sheet may have a basis weight of 35 gsm to 55 gsm, preferably 40 gsm to 50 gsm. In a preferred embodiment, the paper layer of the co-laminate sheet may have a basis weight of 45 gsm.

[0124] The paper layer of the co-laminate sheet may have a thickness of at least 50 micrometers, preferably at least 55 micrometers, more preferably at least 60 micrometers. The paper layer of the co-laminate sheet may have a thickness of 80 micrometers or less, preferably 75 micrometers or less, more preferably 70 micrometers or less.

[0125] The paper layer of the co-laminate sheet may have a thickness of about 50 micrometers to about 80 micrometers, preferably about 55 micrometers to about 75 micrometers, more preferably about 60 micrometers to about 70 micrometers. In a preferred embodiment, the paper layer of the co-laminate sheet may have a thickness of 65 microns.

[0126] The metal layer of the co-laminate sheet may have a basis weight of at least 12 gsm, preferably at least 15 gsm. The metal layer of the co-laminate sheet may have a basis weight of 25 gsm or less, preferably 20 gsm or less. The metal layer of the co-laminate sheet may have a basis weight of 12 gsm to 25 gsm, preferably 15 gsm to 20 gsm. In a preferred embodiment, the metal layer of the co-laminate sheet may have a basis weight of 17 gsm.

[0127] The metal layer of the co-laminate sheet may have a thickness of at least 2 micrometers, preferably at least 3 micrometers, more preferably at least 5 micrometers. The metal layer of the co-laminate sheet may have a thickness of 15 micrometers or less, preferably 12 micrometers or less, more preferably 10 micrometers or less.

[0128] The metal layer of the co-laminate sheet may have a thickness of about 2 micrometers to about 15 micrometers, preferably about 3 micrometers to about 12 micrometers, more preferably about 5 micrometers to about 10 micrometers. In a preferred embodiment, the metal layer of the co-laminate sheet may have a thickness of 6 microns.

[0129] The wrapper, particularly the rod wrapper, may be a paper wrapper containing PVOH (polyvinyl alcohol) or silicon. The addition of PVOH (polyvinyl alcohol) or silicon may improve the grease barrier properties of the wrapper.

[0130] The PVOH or silicon may be applied to the paper layer as a surface coating, such as disposed on the outer surface of the paper layer of the wrapper surrounding the aerosol-generating rod. The PVOH or silicon may be disposed on the outer surface of the paper layer of the wrapper and may form a layer. The PVOH or silicon may be disposed on the inner surface of the paper layer of the wrapper. The PVOH or silicon may be disposed on the inner surface of the paper layer of the aerosol-generating article and may form a layer. The PVOH or silicon may be disposed on the inner and outer surfaces of the paper layer of the wrapper. The PVOH or silicon may be disposed on the inner and outer surfaces of the paper layer of the wrapper and may form a layer.

[0131] The PVOH or silicon containing paper wrapper may have a basis weight of at least 20 gsm, preferably at least 25 gsm, more preferably at least 30 gsm. The PVOH or silicon containing paper wrapper may have a basis weight of 50 gsm or less, 45 gsm or less, more preferably 40 gsm or less. The PVOH or silicon containing paper wrapper may have a basis weight of 20 gsm to 50 gsm, preferably 25 gsm to 45 gsm, more preferably 30 gsm to 40 gsm. In a particularly preferred embodiment, the PVOH or silicon containing paper wrapper may have a basis weight of about 35 gsm.

[0132] The PVOH or silicon-containing paper wrapper may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, more preferably at least 35 micrometers. The PVOH or silicon-containing paper wrapper may have a thickness of 50 micrometers or less, preferably 45 micrometers or less, more preferably 40 micrometers or less. The PVOH or silicon-containing paper wrapper may have a thickness of 25 micrometers to 50 micrometers, preferably 30 micrometers to 45 micrometers, more preferably 35 micrometers to 40 micrometers. In a particularly preferred embodiment, the PVOH or silicon-containing paper wrapper may have a thickness of 37 micrometers.

[0133] The wrapper, and in particular the core wrapper, may include a flame retardant composition that includes one or more flame retardant compounds. The term "flame retardant compound" is used herein to describe a compound that, when added to or otherwise incorporated into a carrier substrate, such as a paper or plastic compound, provides various degrees of flammability protection to the carrier substrate. In fact, the flame retardant compound may be activated by the presence of an ignition source and is adapted to prevent or slow down the further development of ignition by a variety of different physical and chemical mechanisms.

[0134] The flame retardant composition may typically further comprise one or more non-flame retardant compounds, i.e., one or more compounds (such as solvents, excipients, fillers, etc.) that do not actively contribute to providing flammability protection to the carrier substrate, but are used to facilitate application of the flame retardant compound(s) onto or into the wrapper, or both. Some of the non-flame retardant compounds of the flame retardant composition (such as solvents) may be volatile and evaporate from the wrapper as it dries after the flame retardant composition is applied onto or into the wrapping substrate, or both. Thus, such non-flame retardant compounds may no longer be present, or may only be detectable in trace amounts, in the wrapper of the aerosol-generating article, although they form part of the formulation of the flame retardant composition.

[0135] Numerous suitable flame retardant compounds are known to those skilled in the art. In particular, several flame retardant compounds and formulations suitable for the treatment of cellulosic materials are known and disclosed and may find use in the manufacture of wrappers for aerosol-generating articles according to the present invention.

[0136] For example, the flame retardant composition may comprise a polymer and a mixed salt based on at least one mono-, di-, and / or tricarboxylic acid, at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid, and a hydroxide or salt of an alkali or alkaline earth metal, where the at least one mono-, di-, and / or tricarboxylic acid and the hydroxide or salt form a carboxylate and at least one polyphosphoric acid, and the pyrophosphoric acid and / or phosphoric acid and the hydroxide or salt form a phosphate. Preferably, the flame retardant composition further comprises a carbonate of an alkali or alkaline earth metal. Alternatively, the flame retardant composition comprises at least one C 10 The cellulose may be modified with the above fatty acids, tall oil fatty acid (TOFA), phosphorylated linseed oil, or phosphorylated downstream corn oil. Preferably, the cellulose may be modified with at least one C 10 The fatty acids are selected from the group consisting of capric acid, myristic acid, palmitic acid, and combinations thereof.

[0137] In a wrapper comprising a flame retardant composition suitable for use in an aerosol-generating article according to the present invention, the flame retardant composition may be provided within a treated portion of the wrapper. This means that the flame retardant composition is applied on or in a corresponding portion of the wrapping substrate, or both. Thus, in the treated portion, the wrapper has a total dry basis weight greater than the dry basis weight of the wrapping substrate. The treated portion of the wrapper may extend over at least about 10 percent of the outer surface area of ​​the core portion surrounded by the wrapper, preferably at least about 20 percent of the outer surface area of ​​the core portion surrounded by the wrapper, more preferably at least about 40 percent of the outer surface area of ​​the core portion, and even more preferably at least about 60 percent of the outer surface area of ​​the core portion. Most preferably, the treated portion of the wrapper extends over at least about 80 percent of the outer surface area of ​​the core portion. In a particularly preferred embodiment, the treated portion of the wrapper extends over at least about 90, or even 95 percent of the outer surface area of ​​the core portion. Most preferably, the treated portion of the wrapper extends over substantially the entire outer surface area of ​​the core portion.

[0138] The wrapper comprising the flame retardant composition may have a basis weight of at least 20 gsm, preferably at least 25 gsm, more preferably at least 30 gsm. The wrapper comprising the flame retardant composition may have a basis weight of 45 gsm or less, preferably 40 gsm or less, more preferably 35 gsm or less. The wrapper comprising the flame retardant composition may have a basis weight of 20 gsm to 45 gsm, preferably 25 gsm to 40 gsm, more preferably 30 gsm to 35 gsm. In some preferred embodiments, the wrapper comprising the flame retardant composition may have a basis weight of 33 gsm.

[0139] The wrapper containing the flame retardant composition may have a thickness of at least 25 micrometers, preferably at least 30 micrometers, and even more preferably 35 micrometers. The wrapper containing the flame retardant composition may have a thickness of 50 micrometers or less, preferably 45 micrometers or less, and even more preferably 40 micrometers or less. In some embodiments, the wrapper containing the flame retardant composition may have a thickness of 37 micrometers.

[0140] In some embodiments, the aerosol-generating article may include a susceptor element disposed within the core portion and thermally coupled to the aerosol-generating substrate. As used herein, the term "susceptor element" refers to an element that includes a material capable of converting electromagnetic energy into heat. When the susceptor element is located within an alternating electromagnetic field, the susceptor is heated. Heating of the susceptor element may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0141] In the aerosol-generating article according to the invention, the annular portion advantageously separates the susceptor elements provided in the core portion from the periphery of the aerosol-generating article, e.g., the core wrapper. This is beneficial in that accidental self-ignition of the aerosol-generating article due to direct cooperation between the paper-containing core wrapper and misaligned susceptor elements can be prevented. Furthermore, during or immediately after use, the annular portion can act as an insulating barrier between the hot surface of the susceptor elements and the consumer.

[0142] Providing a susceptor element within the core portion also has the advantage that the heat source is internal to the core portion, whereas external heating, i.e., supplying heat by a heating element disposed external to the aerosol-generating article, is less efficient as the annular portion may act as an insulating barrier.

[0143] The susceptor element may be arranged such that when an aerosol-generating article is received within the cavity of the aerosol generating device, the oscillating electromagnetic field generated by the inductor coil induces a current in the susceptor element, heating the susceptor element. In these embodiments, the aerosol generating device is preferably capable of generating a fluctuating electromagnetic field having a magnetic field strength (H field strength) of 1 to 5 kiloamperes per meter (kA / m), preferably 2 to 3 kA / m, for example about 2.5 kA / m. The electrically operated aerosol generating device is preferably capable of generating a fluctuating electromagnetic field having a frequency of 1 to 30 MHz, for example 1 to 10 MHz, for example 5 to 7 MHz.

[0144] The susceptor element may comprise any suitable material. The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to release volatile compounds from the aerosol-forming substrate. Suitable materials for the elongated susceptor element include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Some susceptor elements include metal or carbon. Advantageously, the susceptor element may include or consist of a ferromagnetic material, such as ferritic iron, ferromagnetic steel or stainless steel, ferromagnetic alloys, ferromagnetic particles, and ferrites. A suitable susceptor element may be or include aluminum. The susceptor element preferably includes more than about 5 percent, preferably more than about 20 percent, more preferably more than about 50 percent or more than about 90 percent of ferromagnetic or paramagnetic material. Some elongated susceptor elements may be heated to a temperature of more than about 250 degrees Celsius.

[0145] The susceptor element may comprise a non-metallic core having a metallic layer disposed thereon. For example, the susceptor element may include a ceramic core or a metallic track formed on the outer surface of the substrate.

[0146] In some embodiments, the aerosol generating device may comprise at least one resistive heating element and at least one inductive heating element, hi some embodiments, the aerosol generating device may comprise a combination of resistive and inductive heating elements.

[0147] In use, the heater can be controlled to operate within a defined operating temperature range that is less than the maximum operating temperature. The operating temperature range within the heating chamber (or device cavity) is preferably from about 150 degrees Celsius to about 300 degrees Celsius. The operating temperature range of the heater may be from about 150 degrees Celsius to about 250 degrees Celsius.

[0148] Preferably, the operating temperature range of the heater may be between about 150 degrees Celsius and about 200 degrees Celsius. More preferably, the operating temperature range of the heater may be between about 180 degrees Celsius and about 200 degrees Celsius. Specifically, as described herein, it has been found that optimal and consistent aerosol delivery may be achieved when using an aerosol generating device having an external heater with an operating temperature range of about 180 degrees Celsius to about 200 degrees Celsius with an aerosol-generating article having a relatively low RTD (e.g., having an RTD of the downstream section less than 15 mmH2O).

[0149] The susceptor elements may be in the form of elongated susceptors disposed longitudinally within the aerosol-generating substrate. When used to describe a susceptor element, the term "elongated" means that the susceptor element has a length dimension that is greater than its width dimension or its thickness dimension, e.g., greater than twice its width dimension or its thickness dimension.

[0150] The susceptor may be disposed substantially longitudinally within the core portion, meaning that the length dimension of the elongated susceptor is disposed approximately parallel to the longitudinal axis of the aerosol-generating rod, for example within ±10 degrees of parallel to the longitudinal axis of the aerosol-generating rod. In a preferred embodiment, the elongated susceptor may be positioned at a radially central location within the aerosol-generating rod and extends along the longitudinal axis of the aerosol-generating rod.

[0151] In a particularly preferred embodiment, the susceptor has substantially the same length as the aerosol-generating rod and extends from the upstream end of the core portion to the downstream end of the core portion. The susceptor is preferably in the form of a pin, rod, strip or blade.

[0152] When the susceptor has the form of a strip or blade, the strip or blade has a rectangular shape, preferably having a width of 2 mm to 6 mm, more preferably 2.5 mm to 5.5 mm, even more preferably 3 mm to 5 mm. By way of example, a susceptor in the form of a blade strip may have a width of about 3.75 mm.

[0153] In a preferred embodiment, the elongated susceptor is in the form of a strip or blade, has a substantially rectangular shape, and has a thickness of about 55 micrometers to about 65 micrometers.

[0154] In the aerosol-generating article according to the invention, the aerosol-generating rod further comprises an air-permeable annular portion surrounding the core portion and extending coaxially therewith. The annular portion extends radially from the inner circumference of the annular portion to the outer circumference of the annular portion. The distance between the inner circumference of the annular portion and the outer circumference of the annular portion measured along the radial direction may be described as the thickness of the annular portion.

[0155] The annular portion preferably has a substantially uniform cross-section along the length of the aerosol-generating rod. The cross-section of the annular portion is the area contained between two concentric circles defined by the intersection of the outer and inner circumferences of the annular portion with the transverse cross-section, the radii of the two concentric circles remaining substantially constant along the length of the aerosol-generating rod. Thus, the thickness of the annular portion is preferably substantially constant along the length of the aerosol-generating rod.

[0156] The annular portion and the core portion are preferably the same length.

[0157] The cross-sectional porosity of the annular portion is at least 120 percent of the cross-sectional porosity of the core portion. Preferably, the cross-sectional porosity of the annular portion is at least 130 percent of the cross-sectional porosity of the core portion. More preferably, the cross-sectional porosity of the annular portion is at least 140 percent of the cross-sectional porosity of the core portion. Even more preferably, the cross-sectional porosity of the annular portion is at least 150 percent of the cross-sectional porosity of the core portion.

[0158] In some embodiments, the cross-sectional porosity of the annular portion may be at least 175 percent of the cross-sectional porosity of the core portion, preferably at least 200 percent of the cross-sectional porosity of the core portion.

[0159] In certain embodiments, the cross-sectional porosity of the annular portion is at least 200 percent of the cross-sectional porosity of the core portion, preferably at least 250 percent of the cross-sectional porosity of the core portion, more preferably at least 300 percent of the cross-sectional porosity of the core portion, even more preferably 400 percent of the cross-sectional porosity of the core portion, or 500 percent of the cross-sectional porosity of the core portion, or 600 percent of the cross-sectional porosity of the core portion.

[0160] In some embodiments, the cross-sectional porosity of the annular portion may be between 120 percent and 600 percent of the cross-sectional porosity of the core portion, or between 120 percent and 500 percent of the cross-sectional porosity of the core portion, or between 120 percent and 400 percent of the cross-sectional porosity of the core portion, or between 120 percent and 300 percent of the cross-sectional porosity of the core portion, or between 120 percent and 200 percent of the cross-sectional porosity of the core portion.

[0161] In other embodiments, the cross-sectional porosity of the annular portion may be between 130 percent and 600 percent of the cross-sectional porosity of the core portion, or between 130 percent and 500 percent of the cross-sectional porosity of the core portion, or between 130 percent and 400 percent of the cross-sectional porosity of the core portion, or between 130 percent and 300 percent of the cross-sectional porosity of the core portion, or between 130 percent and 200 percent of the cross-sectional porosity of the core portion.

[0162] In further embodiments, the cross-sectional porosity of the annular portion may be between 140 percent and 600 percent of the cross-sectional porosity of the core portion, or between 140 percent and 500 percent of the cross-sectional porosity of the core portion, or between 140 percent and 400 percent of the cross-sectional porosity of the core portion, or between 140 percent and 300 percent of the cross-sectional porosity of the core portion, or between 140 percent and 200 percent of the cross-sectional porosity of the core portion.

[0163] In further embodiments, the cross-sectional porosity of the annular portion may be between 150 percent and 600 percent of the cross-sectional porosity of the core portion, or between 150 percent and 500 percent of the cross-sectional porosity of the core portion, or between 150 percent and 400 percent of the cross-sectional porosity of the core portion, or between 150 percent and 300 percent of the cross-sectional porosity of the core portion, or between 150 percent and 200 percent of the cross-sectional porosity of the core portion.

[0164] The cross-sectional porosity of the annular portion may be up to 0.99.

[0165] The cross-sectional porosity of the annular portion is preferably less than 0.95. More preferably, the cross-sectional porosity of the annular portion is less than 0.90. Even more preferably, the cross-sectional porosity of the annular portion is less than 0.85. This is beneficial in that it can ensure a certain structural strength of the annular portion and the rod as a whole.

[0166] The cross-sectional porosity of the annular portion may be at least 0.3. Preferably, the cross-sectional porosity of the annular portion is at least 0.35. More preferably, the cross-sectional porosity of the annular portion is at least 0.4. Even more preferably, the cross-sectional porosity of the annular portion is at least 0.45.

[0167] In some embodiments, the cross-sectional porosity of the annular portion is 0.3 to 0.95, preferably 0.35 to 0.95, more preferably 0.4 to 0.95, and even more preferably 0.5 to 0.95. In other embodiments, the cross-sectional porosity of the annular portion is 0.3 to 0.90, preferably 0.35 to 0.90, more preferably 0.4 to 0.90, and even more preferably 0.5 to 0.90. In further embodiments, the cross-sectional porosity of the annular portion is 0.3 to 0.85, preferably 0.35 to 0.85, more preferably 0.4 to 0.85, and even more preferably 0.5 to 0.85.

[0168] Due to these low porosity values, the annular portion exhibits a significantly lower resistance to withdrawal (RTD) than the RTD of the core portion.

[0169] In an aerosol-generating article according to the invention, the RTD of the annular portion is preferably less than 65 millimeters HO. More preferably, the RTD of the annular portion is preferably less than 60 millimeters HO. Even more preferably, the RTD of the annular portion is preferably less than 55 millimeters HO.

[0170] The RTD of the annular portion may be at least 5 millimeters of H2O. Preferably, the RTD of the annular portion is at least 10 millimeters of H2O. More preferably, the RTD of the annular portion is at least 20 millimeters of H2O. Even more preferably, the RTD of the annular portion is at least 30 millimeters of H2O.

[0171] In some embodiments, the RTD of the annular portion is between 10 millimeters H2O and 65 millimeters H2O, preferably between 10 millimeters H2O and 60 millimeters H2O, more preferably between 10 millimeters H2O and 55 millimeters H2O. In other embodiments, the RTD of the annular portion is between 20 millimeters H2O and 65 millimeters H2O, preferably between 20 millimeters H2O and 60 millimeters H2O, more preferably between 20 millimeters H2O and 55 millimeters H2O. In further embodiments, the RTD of the annular portion is between 30 millimeters H2O and 65 millimeters H2O, preferably between 30 millimeters H2O and 60 millimeters H2O, more preferably between about 30 millimeters H2O and 55 millimeters H2O.

[0172] The annular portion may comprise a porous material, such as a foam, or a fibrous material, such as a nonwoven material.

[0173] The annular portion may include a fibrous material. In some embodiments, the annular portion includes a plurality of fibers, preferably linear axially oriented fibers. As used herein, the expression "linear axially oriented fibers" is used to describe a plurality of fibers that are substantially aligned with each other along the axial direction of the annular portion or the aerosol drawing direction. This is in contrast to multidirectionally oriented, or randomly oriented, or multidirectionally and randomly oriented fibers, i.e., a plurality of primarily unaligned fibers having a plurality of different or random orientations, including both parallel and perpendicular to the axial direction or the aerosol drawing direction, or a plurality of different and random orientations.

[0174] Suitable fibers are known to those skilled in the art. Preferably, the annular portion comprises fibers selected from cellulose acetate fibers, polylactic acid (PLA) fibers, polypropylene fibers, poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHVB) fibers, rayon fibers, viscose fibers, regenerated cellulose fibers, and combinations thereof.

[0175] In certain embodiments, the annular portion may include two or more longitudinal segments of tow material, with the tow material of adjacent ones of the two or more longitudinal segments bonded together at least along the longitudinal edges of the segments to form an integral annular portion, and at least two or all of the segments may be formed from the same tow.

[0176] Preferably, the annular portion comprises fibers having a denier per filament (dpf) of at least 3.0. More preferably, the annular portion comprises fibers having a dpf of at least 5.0. More preferably, the annular portion comprises fibers having a dpf of at least 6.0.

[0177] Preferably, the annular portion comprises fibers having a dpf of 15.0 or less. More preferably, the annular portion comprises fibers having a dpf of 10.0 or less. Even more preferably, the annular portion comprises fibers having a dpf of 9.0 or less.

[0178] In some embodiments, the annular portion comprises fibers having a dpf of 3.0 to 15.0, preferably 3.0 to 10.0, more preferably 3.0 to 9.0. In other embodiments, the annular portion comprises fibers having a dpf of 5.0 to 15.0, preferably 5.0 to 10.0, more preferably 5.0 to 9.0. In further embodiments, the annular portion comprises fibers having a dpf of 6.0 to 15.0, preferably 6.0 to 10.0, more preferably 6.0 to 9.0.

[0179] In some embodiments, the fibers may have a Y-shaped cross section.

[0180] The outer diameter of the annular portion may be up to 10 millimeters. Preferably, the outer diameter of the annular portion is less than 9 millimeters. More preferably, the outer diameter of the annular portion is less than 7.7 millimeters.

[0181] In an aerosol-generating article according to the invention, the thickness of the annular portion may be at least 0.5 millimeters. Preferably, the thickness of the annular portion is at least 1.0 millimeters. More preferably, the thickness of the annular portion is at least 1.5 millimeters. The thickness of the annular portion may be less than 5.0 millimeters. Preferably, the thickness of the annular portion is less than 4.0 millimeters. More preferably, the thickness of the annular portion is less than 3.5 millimeters. Even more preferably, the thickness of the annular portion is less than 3.0 millimeters.

[0182] In some embodiments, the thickness of the annular portion is between 0.5 millimeters and 4 millimeters, preferably between 0.5 millimeters and 3.5 millimeters, and more preferably between 0.5 millimeters and 3 millimeters. In other embodiments, the thickness of the annular portion is between 1.0 millimeters and 4 millimeters, preferably between 1.0 millimeters and 3.5 millimeters, and more preferably between 1.0 millimeters and 3 millimeters. In further embodiments, the thickness of the annular portion is between 1.5 millimeters and 4 millimeters, preferably between 1.5 millimeters and 3.5 millimeters, and more preferably between 1.5 millimeters and 3 millimeters.

[0183] In preferred embodiments, the annular portion radially abuts the core portion. In other words, the annular portion immediately surrounds the core portion. In these embodiments, the inner circumference of the annular portion is immediately adjacent to the outer circumference of the cylindrical core portion, e.g., as defined by the outer surface of the core wrapper, and thus the annular portion extends radially from the outer circumference of the cylindrical core portion to the outer circumference of the annular portion. Thus, the inner diameter of the annular portion substantially matches the outer diameter of the core portion.

[0184] As briefly explained above, an aerosol-generating article according to the present invention is provided downstream of an aerosol-generating rod and comprises a downstream section abutting the downstream end of the aerosol-generating rod.

[0185] The downstream section may have any length. The downstream section may have a length of at least 10 millimeters. For example, the downstream section may have a length of at least 15 millimeters, at least 20 millimeters, at least 25 millimeters, or at least 30 millimeters.

[0186] Providing a downstream section having a length greater than the above values ​​advantageously allows space for the aerosol to cool and condense before reaching the consumer, which also ensures that the user is away from the heating element when the aerosol-generating article is used in conjunction with an aerosol generating device.

[0187] The downstream section may have a length of less than 80 millimeters. For example, the downstream section may have a length of 70 millimeters or less, 60 millimeters or less, 50 millimeters or less, or 40 millimeters or less.

[0188] The ratio of the length of the downstream section to the length of the aerosol-generating rod may be between 1.0 and 4.5. Preferably, the ratio of the length of the downstream section to the length of the aerosol-generating rod is at least 1.25, more preferably at least 1.5, even more preferably at least 2.0. In a preferred embodiment, the ratio of the length of the downstream section to the length of the aerosol-generating rod is equal to or less than 4.0, preferably less than 3.5, even more preferably less than 3.0.

[0189] The length of the downstream section corresponds substantially to the sum of the lengths of the individual components that form the downstream section.

[0190] In a preferred embodiment, the downstream section comprises a hollow tubular element defining an internal cavity, the upstream end of the hollow tubular element abutting the downstream end of the aerosol-generating rod. In such an embodiment, the inner diameter of the annular portion is preferably smaller than the inner diameter of the hollow tubular element, such that the annular portion is in direct fluid communication with the internal cavity of the hollow tubular element.

[0191] In the aerosol-generating article according to the invention, the hollow tubular element may have a length of at least 5 mm. Preferably, the hollow tubular element has a length of at least 10 mm. More preferably, the hollow tubular element has a length of at least 12 mm. Even more preferably, the hollow tubular element has a length of at least 15 mm.

[0192] Preferably, the length of the hollow tubular element is 45 millimeters or less. More preferably, the length of the hollow tubular element is 40 millimeters or less. Even more preferably, the length of the hollow tubular element is 40 millimeters or less.

[0193] In a preferred embodiment, the length of the hollow tubular element is 35 millimeters or less. More preferably, the length of the hollow tubular element is 30 millimeters or less. Even more preferably, the length of the hollow tubular element is 25 millimeters or less. In a particularly preferred embodiment, the length of the hollow tubular element is 22 millimeters or less.

[0194] In some embodiments, the length of the hollow tubular element is between 10 mm and 45 mm, preferably between 10 mm and 40 mm, more preferably between 10 mm and 35 mm, even more preferably between 10 mm and 30 mm. In particularly preferred embodiments, the length of the hollow tubular element is between 10 mm and 25 mm, preferably between 10 mm and 22 mm.

[0195] In other embodiments, the length of the hollow tubular element is between 12 mm and 45 mm, preferably between 12 mm and 40 mm, more preferably between 12 mm and 35 mm, even more preferably between 12 mm and 30 mm.In a particularly preferred embodiment, the length of the hollow tubular element is between 12 mm and 25 mm, preferably between 12 mm and 22 mm.

[0196] In a further embodiment, the length of the hollow tubular element is between 15 mm and 45 mm, preferably between 15 mm and 40 mm, more preferably between 15 mm and 35 mm, even more preferably between 15 mm and 30 mm.In a particularly preferred embodiment, the length of the hollow tubular element is between 15 mm and 25 mm, preferably between 15 mm and 22 mm.

[0197] The hollow tubular element may have an inner diameter of at least 3.5 millimeters. For example, the hollow tubular element may have an inner diameter of at least 4 millimeters, at least 5 millimeters, or at least 6 millimeters.

[0198] Providing a hollow tubular element with an inner diameter as set out above may advantageously provide the hollow tubular element with sufficient stiffness and strength.

[0199] The hollow tubular element may have an inner diameter of 7 millimeters or less. For example, the hollow tubular element may have an inner diameter of about 6.5 millimeters or less.

[0200] Providing a hollow tubular element with an inner diameter as set out above may advantageously reduce the resistance to pulling out the hollow tubular element.

[0201] The hollow tubular element may have an inner diameter of 3.5 mm to 7 mm, 4 mm to 7 mm, about 5 mm to 7 mm, or 6 mm to 7 mm. The hollow tubular element may have an inner diameter of 3.5 mm to 6.5 mm, 4 mm to 6.5 mm, about 5 mm to 6.5 mm, or 6 mm to about 6.5 mm.

[0202] The outer diameter of the hollow tubular element preferably substantially matches the outer diameter of the annular portion, which may also be approximately equal to the outer diameter of the aerosol-generating article.

[0203] The ratio between the inner diameter of the hollow tubular element and the outer diameter of the hollow tubular element may be at least about 0.8. For example, the ratio between the inner diameter of the hollow tubular element and the outer diameter of the hollow tubular element may be at least about 0.85, at least about 0.9, or at least about 0.95.

[0204] The ratio between the inner diameter of the hollow tubular element and the outer diameter of the hollow tubular element may be about 0.99 or less. For example, the ratio between the inner diameter of the hollow tubular element and the outer diameter of the hollow tubular element may be about 0.98 or less.

[0205] The ratio between the inner diameter of the hollow tubular element and the outer diameter of the hollow tubular element may be about 0.97.

[0206] Providing a relatively large inner diameter advantageously reduces the resistance to pulling out the hollow tubular element.

[0207] The lumen of the hollow tubular element may have any cross-sectional shape. The lumen of the hollow tubular element may have a circular cross-sectional shape.

[0208] The hollow tubular element may be formed from any material. For example, the hollow tubular element may include cellulose acetate tow. When the hollow tubular element includes cellulose acetate tow, the hollow tubular element may have a thickness of about 0.1 millimeter to about 1 millimeter. The hollow tubular element may have a thickness of about 0.5 millimeter.

[0209] When the hollow tubular element comprises cellulose acetate tow, the cellulose acetate tow may have a dpf of from about 2 to about 4, and a total denier of from about 25 to about 40.

[0210] The hollow tubular element may comprise paper. The hollow tubular element may comprise at least one layer of paper. The paper may be very stiff paper. The paper may be a crimped paper, such as crimped heat-resistant paper or crimped parchment paper. The paper may be cardboard. The hollow tubular element may be a paper tube. The hollow tubular element may be a tube formed from spirally wound paper. The hollow tubular element may be formed from multiple layers of paper. The paper may have a basis weight of at least about 50 grams per square meter, at least about 60 grams per square meter, at least about 70 grams per square meter, or at least about 90 grams per square meter.

[0211] When the tubular element comprises paper, the paper may have a thickness of at least about 50 micrometers. For example, the paper may have a thickness of at least about 70 micrometers, at least about 90 micrometers, or at least about 100 micrometers.

[0212] The hollow tubular element may comprise a polymer. For example, the hollow tubular element may comprise a polymeric film. The polymeric film may comprise a cellulose film. The hollow tubular element may comprise low density polyethylene (LDPE) or polyhydroxyalkanoate (PHA) fibers.

[0213] In embodiments in which the downstream section comprises a hollow tubular element, the inner diameter of the annular portion is preferably smaller than the inner diameter of the hollow tubular element, such that direct fluid communication is established between the annular portion and the internal cavity defined by the hollow tubular element.

[0214] Therefore, when an aerosol-generating article is not received in an aerosol-generating device or is received in an aerosol-generating device not designed for use with an aerosol-generating article, air drawn into the aerosol-generating rod from the upstream end will flow directly into the cavity of the hollow tubular element, primarily through the annular portion. The RTD encountered by this flow of air along the aerosol-generating article will therefore depend only on any components of the downstream section other than the hollow tubular element, if there is any such component. For example, the overall RTD encountered by this flow of air along the aerosol-generating article may depend only on the RTD of the mouthpiece, which will be described in more detail below.

[0215] In some embodiments, the aerosol-generating article according to the invention comprises ventilation zones at locations along the hollow tubular element that may allow cool air from outside the aerosol-generating article to enter the interior cavity of the hollow tubular element.

[0216] Aerosol-generating articles typically have a breathability level of at least about 10 percent, preferably at least about 20 percent.

[0217] In preferred embodiments, the aerosol-generating article has a breathability level of at least about 20 percent, or 25 percent, or 30 percent. More preferably, the aerosol-generating article has a breathability level of at least about 35 percent.

[0218] Preferably, the aerosol-generating article has a breathability level of less than about 80 percent. More preferably, the aerosol-generating article has a breathability level of less than about 60 percent or less than about 50 percent.

[0219] Aerosol-generating articles generally have a breathability level of from about 10 percent to about 80 percent.

[0220] In some embodiments, the aerosol-generating article has a ventilation level of about 20 percent to about 80 percent, preferably about 20 percent to about 60 percent, and more preferably about 20 percent to about 50 percent. In other embodiments, the aerosol-generating article has a ventilation level of about 25 percent to about 80 percent, preferably about 25 percent to about 60 percent, and more preferably about 25 percent to about 50 percent. In other embodiments, the aerosol-generating article has a ventilation level of about 30 percent to about 80 percent, preferably about 30 percent to about 60 percent, and more preferably about 30 percent to about 50 percent.

[0221] In particularly preferred embodiments, the aerosol-generating article has a breathability level of about 40 percent to about 50 percent. In some particularly preferred embodiments, the aerosol-generating article has a breathability level of about 45 percent.

[0222] Without wishing to be bound by theory, the inventors have found that the temperature reduction caused by admitting cooler outside air into a hollow tubular segment can have a beneficial effect on the nucleation and growth of aerosol particles.

[0223] The formation of aerosols from gaseous mixtures containing various chemical species depends on a delicate interplay between nucleation, evaporation, condensation and even fusion, which accounts for the changes in vapor 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 remain coherent for a long time with a sufficient probability (e.g., one in two). These molecules represent a kind of critical, threshold molecular clusters in the temporary molecular aggregates, which means that smaller molecular clusters are generally prone to break down into the gas phase rather quickly, while larger clusters are generally prone to growth. These critical clusters are identified as the main nucleation cores from which droplets are expected to grow due to the condensation of molecules from the vapor. It is assumed that freshly nucleated raw droplets appear with a certain original diameter and may then grow by several orders of magnitude. This may be facilitated and enhanced by the rapid cooling of the surrounding vapor, which induces the condensation. In this regard, it is helpful to keep in mind that evaporation and condensation are two aspects of one and the same mechanism: gas-liquid mass transfer. Evaporation involves the net mass transfer from the droplets to the gas phase, while condensation is the net mass transfer from the gas phase to the droplet phase. Evaporation (or condensation) causes the droplets to shrink (or grow), but the number of droplets remains unchanged.

[0224] In this scenario (when the scenario is further complicated by fusion phenomena), the temperature and rate of cooling may play an important role in determining how the system responds. In general, different cooling rates may lead to significantly different temperature behaviors with respect to the formation of the liquid phase (droplets), since the nucleation process is typically nonlinear. Without wishing to be bound by theory, it is hypothesized that cooling can cause a rapid increase in the number of condensed droplets, followed by a short-term strong increase in this growth (nucleation burst). This nucleation burst appears to be more pronounced at lower temperatures. Furthermore, it appears that a faster cooling rate may favor the onset of early nucleation. In contrast, a decrease in the cooling rate appears to have a favorable effect on the final size that the aerosol droplets eventually reach.

[0225] Thus, the rapid cooling induced by the inclusion of ambient air in the hollow tubular segment can be used to favor favorable nucleation and growth of aerosol droplets, however, at the same time, the inclusion of ambient air in the hollow tubular segment has the direct drawback of diluting the aerosol stream delivered to the consumer.

[0226] The inventors have surprisingly found that the dilution effect on the aerosol (which may in particular be assessed by measuring the effect on the delivery of the aerosol former (such as glycerol) contained in the aerosol-generating substrate) is advantageously minimized at aeration levels within the ranges mentioned above. In particular, aeration levels of 25 percent to 50 percent, and even more preferably 28 to 42 percent, have been found to lead to particularly satisfactory values ​​of glycerin delivery. At the same time, the degree of nucleation, and consequently the delivery of nicotine and aerosol former (e.g., glycerol), are enhanced.

[0227] The peripheral wall thickness (in other words, the wall thickness) of the hollow tubular element may be at least about 100 micrometers. The wall thickness of the hollow tubular element may be at least about 150 micrometers. The wall thickness of the hollow tubular element may be at least about 200 micrometers, preferably at least about 250 micrometers, and even more preferably at least about 500 micrometers (or 0.5 mm).

[0228] The wall thickness of the hollow tubular element may be 2 millimeters or less, preferably 1.5 millimeters or less, even more preferably 1.25 mm or less. The wall thickness of the hollow tubular element may be 1 millimeter or less. The wall thickness of the hollow tubular element may be 500 micrometers or less.

[0229] The wall thickness of the hollow tubular element may be between 100 micrometers and 2 millimeters, preferably between 150 micrometers and 1.5 millimeters, and even more preferably between 200 micrometers and 1.25 millimeters.

[0230] The wall thickness of the hollow tubular element may preferably be about 250 micrometers (0.25 mm).

[0231] Keeping the thickness of the peripheral wall of the hollow tubular element relatively low ensures that the overall internal volume of the hollow tubular element (which is made available for the aerosol to initiate the nucleation process as soon as the aerosol components leave the rod of the aerosol-generating substrate) and the cross-sectional surface area of ​​the hollow tubular element are effectively maximized, while at the same time ensuring that the hollow tubular element has the necessary structural strength to provide some support to the aerosol-generating rod as well as to prevent collapse of the aerosol-generating article, and that the RTD of the hollow tubular element is minimized. It is understood that a larger value of the cross-sectional surface area of ​​the cavity of the hollow tubular element is associated with a reduced speed of the aerosol flow along the aerosol-generating article, which is also expected to favor the nucleation of the aerosol. Furthermore, by utilizing a hollow tubular element with a relatively low thickness, it appears possible to substantially prevent the diffusion of the vent air before it comes into contact with and mixes with the aerosol flow, which is also understood to be more favorable for the nucleation phenomenon. Indeed, by providing more controllably localized cooling of the stream of volatilized species, it is possible to enhance the effect of cooling on the formation of new aerosol particles.

[0232] The ventilation zone may include a first line of perforations surrounding the hollow tubular element. In some embodiments, the ventilation zone may include two circumferential rows of perforations. For example, the perforations may be formed online during manufacture of the aerosol-generating article. Each circumferential row of perforations may include from about 5 to about 40 perforations, for example, each circumferential row of perforations may include from about 8 to about 30 perforations.

[0233] Where the aerosol-generating article comprises a combined plug wrap, the ventilation zone preferably comprises at least one corresponding circumferential row of perforations through a portion of the combined plug wrap. These may be formed on-line during manufacture of the smoking article. Preferably, the one or more circumferential rows of perforations through the portion of the combined plug wrap are substantially aligned with the one or more rows of perforations through the downstream section.

[0234] Where the aerosol-generating article comprises a strip of tipping paper, the strip of tipping paper extending across one or more circumferential rows of perforations in the downstream section, the ventilation zone preferably comprises at least one corresponding circumferential row of perforations provided through the strip of tipping paper, which may be formed on-line during manufacture of the smoking article. Preferably, the one or more circumferential rows of perforations provided through the strip of tipping paper are substantially aligned with the one or more rows of perforations through the downstream section.

[0235] The ventilation zone may be located anywhere along the hollow tubular element.

[0236] In some embodiments, the ventilation zone may be located at least 8 millimeters from the downstream end of the aerosol-generating article. For example, the ventilation zone may be located at least 10 millimeters, at least 12 millimeters, or at least 15 millimeters from the downstream end of the aerosol-generating article. Locating the first ventilation zone as outlined above may advantageously prevent the first ventilation zone from being blocked by the consumer's mouth or lips during use of the aerosol-generating article.

[0237] The ventilation zone may be located 25 millimeters or less from the downstream end of the aerosol-generating article. For example, the ventilation zone may be located 20 millimeters from the downstream end of the aerosol-generating article. Locating the ventilation zone as outlined above may advantageously prevent the ventilation zone from becoming blocked when the aerosol-generating article is inserted into an aerosol generating device.

[0238] The ventilation zone may be located at least 2 millimeters from the upstream end of the hollow tubular element. For example, the ventilation zone may be located at least 3 millimeters from the upstream end of the hollow tubular element, or at least 4 millimeters from the upstream end of the hollow tubular element, or at least 5 millimeters from the upstream end of the hollow tubular element.

[0239] In some embodiments, the ventilation zone may be located less than 20 millimeters from the downstream end of the hollow tubular element, preferably less than 18 millimeters from the downstream end of the hollow tubular element, more preferably less than 16 millimeters from the downstream end of the hollow tubular element, and even more preferably less than 14 millimeters from the downstream end of the hollow tubular element.

[0240] In the context of the present invention, the hollow tubular element provides an unrestricted flow channel. This means that the hollow tubular element provides a negligible level of resistance to withdrawal (RTD). The term "negligible level of RTD" is used to describe an RTD of less than 1 mmH2O per 10 millimeters of length of hollow tubular element or hollow tubular element, preferably less than 0.4 mmH2O per 10 millimeters of length of hollow tubular element or hollow tubular element, more preferably less than 0.1 mmH2O per 10 millimeters of length of hollow tubular element or hollow tubular element.

[0241] Unless otherwise specified, the resistance to draw (RTD) of a component or aerosol-generating article is measured in accordance with ISO 6565-2015. RTD refers to the pressure required to force air through the entire length of the component. The terms "pressure drop" or "draw resistance" of a component or article may also refer to "resistance to draw." Such terms typically refer to measurements in accordance with ISO 6565-2015 being performed under test at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr), and a relative humidity of about 60 percent, with a volumetric flow rate of about 17.5 milliliters per second at the output or downstream end of the component being measured.

[0242] Preferably, the RTD of the hollow tubular element is about 10 millimeters H2O or less. More preferably, the RTD of the hollow tubular element is about 5 millimeters H2O or less. Even more preferably, the RTD of the hollow tubular element is about 2.5 millimeters H2O or less. Even more preferably, the RTD of the hollow tubular element is about 2 millimeters H2O or less. Even more preferably, the RTD of the hollow tubular element is about 1 millimeter H2O or less.

[0243] The RTD of the hollow tubular element can be at least 0 millimeters H2O, or at least about 0.25 millimeters H2O, or at least about 0.5 millimeters H2O, or at least about 1 millimeter H2O.

[0244] In some preferred embodiments, the RTD of the hollow tubular element is about 0 millimeters H2O to about 10 millimeters H2O, preferably about 0.25 millimeters H2O to about 10 millimeters H2O, and preferably about 0.5 millimeters H2O to about 10 millimeters H2O. In other embodiments, the RTD of the hollow tubular element is about 0 millimeters H2O to about 5 millimeters H2O, preferably about 0.25 millimeters H2O to about 5 millimeters H2O, and preferably about 0.5 millimeters H2O to about 5 millimeters H2O. In other embodiments, the RTD of the hollow tubular element is about 1 millimeters H2O to about 5 millimeters H2O. In further embodiments, the RTD of the hollow tubular element is about 0 millimeters H2O to about 2.5 millimeters H2O, preferably about 0.25 millimeters H2O to about 2.5 millimeters H2O, and more preferably about 0.5 millimeters H2O to about 2.5 millimeters H2O. In a further embodiment, the RTD of the hollow tubular element is from about 0 millimeters HO to about 2 millimeters HO, preferably from about 0.25 millimeters HO to about 2 millimeters HO, and more preferably from about 0.5 millimeters HO to about 2 millimeters HO. In a particularly preferred embodiment, the RTD of the hollow tubular element is about 0 millimeters HO.

[0245] In the aerosol-generating article according to the invention, the overall RTD of the article depends essentially on the RTD of the aerosol-generating rod, and may also optionally depend on the RTD of other components of the downstream section, such as the mouthpiece, as described below. This is because the hollow tubular segment is substantially empty, and therefore only contributes substantially insignificantly to the overall RTD of the aerosol-generating article. Therefore, the internal cavity of the hollow tubular element should not contain any components that would impede the longitudinal air flow. It is preferred that the internal cavity is substantially empty.

[0246] In practice, the annular portion does not contribute substantially to the overall RTD of the article, so that the overall RTD of the article depends primarily on components of the downstream section other than the core portion and, optionally, the hollow tubular element.

[0247] In an aerosol-generating article according to the invention, the downstream section may comprise a mouthpiece element, hi some embodiments, the downstream section comprises a mouthpiece element downstream of the hollow tubular element, the article further comprising a wrapper surrounding the aerosol-generating rod, the hollow tubular element, and the mouthpiece.

[0248] The mouthpiece element may be located immediately downstream of the hollow tubular element, and thus may extend from the downstream end of the hollow tubular element to the mouth end of the aerosol-generating article, or to the downstream end of the downstream section.

[0249] In such an embodiment, when the hollow tubular element abuts the upstream end of the mouthpiece element, the interior cavity of the hollow tubular element is in direct fluid communication with the mouthpiece element.

[0250] In the aerosol-generating article according to the invention, the mouthpiece element may have a length of at least 5 millimeters. Preferably, the mouthpiece element has a length of at least 10 millimeters. More preferably, the mouthpiece element has a length of at least 12 millimeters. Even more preferably, the mouthpiece element has a length of at least 15 millimeters.

[0251] Preferably, the length of the mouthpiece element is 45 millimeters or less. More preferably, the length of the mouthpiece element is 40 millimeters or less. Even more preferably, the length of the mouthpiece element is 40 millimeters or less.

[0252] In particularly preferred embodiments, the length of the mouthpiece element is 35 millimeters or less. More preferably, the length of the mouthpiece element is 30 millimeters or less. Even more preferably, the length of the mouthpiece element is 25 millimeters or less. In particularly preferred embodiments, the length of the mouthpiece element is 22 millimeters or less.

[0253] In some embodiments, the length of the mouthpiece element is between 10 mm and 45 mm, preferably between 10 mm and 40 mm, more preferably between 10 mm and 35 mm, even more preferably between 10 mm and 30 mm.In particularly preferred embodiments, the length of the mouthpiece element is between 10 mm and 25 mm, preferably between 10 mm and 22 mm.

[0254] In other embodiments, the length of the mouthpiece element is between 12 mm and 45 mm, preferably between 12 mm and 40 mm, more preferably between 12 mm and 35 mm, even more preferably between 12 mm and 30 mm.In particularly preferred embodiments, the length of the mouthpiece element is between 12 mm and 25 mm, preferably between 12 mm and 22 mm.

[0255] In a further embodiment, the length of the mouthpiece element is between 15 mm and 45 mm, preferably between 15 mm and 40 mm, more preferably between 15 mm and 35 mm, even more preferably between 15 mm and 30 mm.In a particularly preferred embodiment, the length of the mouthpiece element is between 15 mm and 25 mm, preferably between 15 mm and 22 mm.

[0256] Preferably, the outer diameter of the mouthpiece element substantially matches the outer diameter of the annular portion, or the outer diameter of the hollow tubular element, or both.

[0257] The mouthpiece element may be formed from a fibrous material.

[0258] The mouthpiece element may be formed of a porous material. The mouthpiece element may be formed of a biodegradable material. The mouthpiece element may be formed of a cellulosic material, such as cellulose acetate. The mouthpiece element may be formed of a polylactic acid-based material. The mouthpiece element may be formed of a bioplastic material, preferably a starch-based bioplastic material. The mouthpiece element may be made by injection molding or extrusion. Bioplastic-based materials are advantageous because they can provide a simple and inexpensive mouthpiece element structure to manufacture with specific and complex cross-sectional profiles, which may include multiple relatively large airflow channels extending through the material of the mouthpiece element, providing suitable RTD characteristics.

[0259] The mouthpiece element may be formed from a sheet of suitable material that is crimped, pleated, assembled, woven, or folded into an element that defines a plurality of longitudinally extending channels. Such sheets of suitable material may be formed of paper, cardboard, polymers such as polylactic acid, or any other cellulosic, paper, or bioplastic-based material. The cross-sectional profile of such a mouthpiece element may exhibit randomly oriented channels.

[0260] The mouthpiece element may be formed in any other suitable manner. For example, the mouthpiece element may be formed from a bundle of longitudinally extending tubes. The longitudinally extending tubes may be formed from polylactic acid. The mouthpiece element may be formed by extrusion, moulding, lamination, injection moulding or shredding of suitable materials. Hence, there is preferably a non-zero pressure drop (or RTD) from the upstream end of the mouthpiece element to the downstream end of the mouthpiece element.

[0261] The mouthpiece element may include at least one filter (airflow) channel extending along the mouthpiece element. The at least one filter airflow channel preferably extends along the entire length of the mouthpiece element. The at least one filter channel may have a substantially circular cross-section. The at least one filter channel may have a substantially Y-shaped or T-shaped cross-section. The mouthpiece element may include a plurality of such filter airflow channels extending along the mouthpiece element. The mouthpiece element may include at least three filter airflow channels. Providing at least one filter airflow channel within the mouthpiece element enables the mouthpiece element to meet a particular RTD value.

[0262] The resistance to draw (RTD) of the mouthpiece element may be at least about 0 mmH2O. The RTD of the mouthpiece element may be at least about 3 mmH2O. The RTD of the mouthpiece element may be at least about 6 mmH2O.

[0263] The RTD of the mouthpiece element may be about 12 mmH2O or less. The RTD of the mouthpiece element may be about 11 mmH2O or less. The RTD of the mouthpiece element may be about 10 mmH2O or less.

[0264] The resistance to withdrawal of the mouthpiece element may be about 0 mmH2O or more and less than about 12 mmH2O. Preferably, the resistance to withdrawal of the mouthpiece element may be about 3 mmH2O or more and less than about 12 mmH2O. The resistance to withdrawal of the mouthpiece element may be about 0 mmH2O or more and less than about 11 mmH2O. Even more preferably, the resistance to withdrawal of the mouthpiece element may be about 3 mmH2O or more and less than about 11 mmH2O. Even more preferably, the resistance to withdrawal of the mouthpiece element may be about 6 mmH2O or more and less than about 10 mmH2O. Preferably, the resistance to withdrawal of the mouthpiece element may be about 8 mmH2O.

[0265] The aerosol-generating article may have a total length of from about 30 millimeters to about 110 millimeters.

[0266] Preferably, the overall length of an aerosol-generating article according to the invention is at least about 30 millimeters. More preferably, the overall length of an aerosol-generating article according to the invention is at least about 40 millimeters. Even more preferably, the overall length of an aerosol-generating article according to the invention is at least about 42 millimeters.

[0267] Preferably, the overall length of an aerosol-generating article according to the invention is 90 mm or less. More preferably, the overall length of an aerosol-generating article according to the invention is 80 mm or less. Even more preferably, the overall length of an aerosol-generating article according to the invention is 70 mm or less.

[0268] In some embodiments, the overall length of the aerosol-generating article is preferably between 30 mm and 90 mm, more preferably between 40 mm and 90 mm, and even more preferably between 42 mm and 90 mm. In other embodiments, the overall length of the aerosol-generating article is between 30 mm and 80 mm, more preferably between 40 mm and 80 mm, and even more preferably between 42 mm and 80 mm. In further embodiments, the overall length of the aerosol-generating article is between 30 mm and 70 mm, more preferably between 40 mm and 70 mm, and even more preferably between 42 mm and 70 mm.

[0269] The outer diameter of the aerosol-generating article may be at least 4 millimeters. Preferably, the outer diameter of the aerosol-generating article is at least 5 millimeters. More preferably, the outer diameter of the aerosol-generating article is at least 6 millimeters. Preferably, the outer diameter of the aerosol-generating article is no greater than 12 millimeters, more preferably no greater than 10 millimeters, even more preferably no greater than 8 millimeters.

[0270] In some embodiments, the outer diameter of the aerosol-generating article is between 4 mm and 12 mm, preferably between 4 mm and 10 mm, more preferably between 4 mm and 8 mm. In other embodiments, the outer diameter of the aerosol-generating article is between 5 mm and 12 mm, preferably between 5 mm and 10 mm, more preferably between 5 mm and 8 mm. In further embodiments, the outer diameter of the aerosol-generating article is between 6 mm and 12 mm, preferably between 6 mm and 10 mm, more preferably between 6 mm and 8 mm.

[0271] The outer diameter of the aerosol-generating article may be substantially constant over the entire length of the aerosol-generating article, or alternatively, different portions of the aerosol-generating article may have different outer diameters.

[0272] In a particularly preferred embodiment, one or more of the components of the aerosol-generating article are individually surrounded by their own wrapper.

[0273] In one embodiment, the aerosol-generating rod and mouthpiece element are individually wound. The aerosol-generating rod and hollow tubular element are then combined together with an outer wrapper. The combined aerosol-generating rod and hollow tubular element are then further combined with a mouthpiece element having its own wrapper by tipping paper.

[0274] Preferably, at least one of the components of the aerosol-generating article is enclosed in a hydrophobic wrapper.

[0275] The term "hydrophobicity" refers to a surface that exhibits water repellent properties. One useful way to determine this is to measure the water contact angle. The "water contact angle" is the angle traditionally measured through a liquid where the liquid / vapor interface meets a solid surface. It quantifies the wettability of a solid surface by a liquid via Young's equation. Hydrophobicity or water contact angle may be determined by utilizing the TAPPI T558 test method, and the results are expressed as the interface contact angle, reported in "degrees", and can range from near zero to near 180 degrees.

[0276] In preferred embodiments, the hydrophobic wrapper comprises a paper layer having a water contact angle of about 30 degrees or greater, preferably about 35 degrees or greater, or about 40 degrees or greater, or about 45 degrees or greater.

[0277] By way of example, the paper layer may comprise PVOH (polyvinyl alcohol) or silicone. The PVOH may be applied to the paper layer as a surface coating, or the paper layer may comprise a surface treatment that includes PVOH or silicone.

[0278] In one particularly preferred embodiment, an aerosol-generating article according to the invention comprises, in a linear, continuous arrangement, an aerosol-generating rod, a hollow tubular element located immediately downstream from the aerosol-generating rod, a mouthpiece element located immediately downstream from the hollow tubular element, and one or more outer wrappers combining the aerosol-generating rod, the hollow tubular element and the mouthpiece element, the hollow tubular element and the mouthpiece element forming the downstream section of the aerosol-generating article.

[0279] The hollow tubular element may abut against the aerosol generation rod. The mouthpiece element may abut against the hollow tubular element. Preferably, the hollow tubular element abuts against the aerosol generation rod and the mouthpiece element abuts against the hollow tubular element.

[0280] In such a particularly preferred embodiment, the aerosol-generating article has a substantially cylindrical shape and an outer diameter of between 4.9 millimeters and 9 millimeters. In a particularly preferred embodiment, the aerosol-generating article has a substantially cylindrical shape and an outer diameter of between 7.7 millimeters. The overall length of the aerosol-generating article is between 30 millimeters and 75 millimeters, and in a particularly preferred embodiment, is 45 millimeters.

[0281] The aerosol-generating rod has a length between 5 mm and 25 mm. In a particularly preferred embodiment, the aerosol-generating rod has a length of about 11 mm. The hollow tubular element has a length between 5 mm and 35 mm. In a particularly preferred embodiment, the hollow tubular element has a length of about 11 mm. The mouthpiece element has a length between 5 mm and 15 mm. In a particularly preferred embodiment, the mouthpiece has a length of about 22 mm.

[0282] The overall length of the article is between 15 millimeters and 75 millimeters. In a particularly preferred embodiment, the aerosol-generating article has a length of about 45 millimeters.

[0283] The aerosol-generating rod comprises a core portion containing at least one of the types of aerosol-generating substrates mentioned above, preferably a conglomerate of sheets of cut tobacco material or homogenized tobacco material. In a preferred embodiment, the core portion comprises cut tobacco material comprising 13 percent to 18 percent by weight glycerol.

[0284] The aerosol-generating rod includes an annular portion radially abutting the core portion and having an outer diameter that substantially matches the outer diameter of the aerosol-generating article. In a particularly preferred embodiment, the thickness of the annular portion is 1.8 millimeters. The inner diameter of the annular portion substantially matches the outer diameter of the core portion. The annular portion is formed of a plurality of straight, axially extending fibers of at least one of the types described above.

[0285] The hollow tubular elements are in the form of cardboard or cellulose acetate tubes and have an inside diameter of 3.4 mm to 9.5 mm. The peripheral wall thickness of the hollow tube segments is approximately 0.5 mm to 1.8 mm.

[0286] A ventilation zone including a row of circumferential openings is provided along the hollow tubular element between 5 and 30 millimeters from the upstream end of the hollow tubular element.

[0287] The mouthpiece elements are in the form of low density cellulose acetate filter segments.

[0288] As discussed above, the present disclosure also relates to an aerosol generation system comprising an aerosol generating device having a distal end and an oral end. The aerosol generating device may comprise a body. The body or housing of the aerosol generating device may define a device cavity for removably receiving an aerosol-generating article at the oral end of the device. The aerosol generating device may comprise a heating element or heater for heating the aerosol-generating substrate when the aerosol-generating article is received within the device cavity.

[0289] The device cavity may be referred to as the heating chamber of the aerosol-generating device. The device cavity may extend between a distal end and an oral or proximal end. The distal end of the device cavity may be a closed end, and the oral or proximal end of the device cavity may be an open end. The aerosol-generating article may be inserted into the device cavity or heating chamber through the open end of the device cavity. The device cavity may be cylindrical in shape to fit the same shape of the aerosol-generating article.

[0290] The phrase "received within" may refer to the fact that a component or element is fully or partially received within another component or element. For example, the phrase "an aerosol-generating article is received within a device cavity" refers to the aerosol-generating article being fully or partially received within a device cavity of the aerosol-generating article. When the aerosol-generating article is received within the device cavity, the aerosol-generating article may abut a distal end of the device cavity. When the aerosol-generating article is received within the device cavity, the aerosol-generating article may be substantially proximate to the distal end of the device cavity. The distal end of the device cavity may be defined by an end wall.

[0291] The length of the device cavity may be from about 10 mm to about 50 mm. The length of the device cavity may be from about 20 mm to about 40 mm. The length of the device cavity may be from about 25 mm to about 30 mm.

[0292] The length of the device cavity (or heating chamber) may be the same as or longer than the length of the aerosol-generating rod. The length of the device cavity may be such that when an aerosol-generating article is received in the device cavity, the downstream section or a portion thereof is configured to protrude from the device cavity. The length of the device cavity may be such that when an aerosol-generating article is received in the device cavity, a portion of the downstream section (such as a hollow tubular element or a mouthpiece element) is configured to protrude from the device cavity. The length of the device cavity may be such that when an aerosol-generating article is received in the device cavity, a portion of the downstream section (such as a hollow tubular element or a mouthpiece element) is configured to be received in the device cavity.

[0293] The diameter of the device cavity may be about 4 mm to about 10 mm. The diameter of the device cavity may be about 5 mm to about 9 mm. The diameter of the device cavity may be about 6 mm to about 8 mm. The diameter of the device cavity may be about 7 mm to about 8 mm. The diameter of the device cavity may be about 7 mm to about 7.5 mm.

[0294] The diameter of the device cavity may be substantially the same as the diameter of the aerosol-generating article or may be larger. The diameter of the device cavity may be the same as the diameter of the aerosol-generating article to establish a tight fit with the aerosol-generating article.

[0295] The device cavity may be configured to establish a tight fit with an aerosol-generating article received within the device cavity. A tight fit may refer to a sliding fit. The aerosol-generating device may include a peripheral wall. Such a peripheral wall may define the device cavity, or the heating chamber. The peripheral wall defining the device cavity may be configured to engage in a tight fit with an aerosol-generating article received within the device cavity such that, when received within the device, there is substantially no gap or empty space between the peripheral wall defining the device cavity and the aerosol-generating article.

[0296] Such an airtight fit may establish an airtight fit or configuration between the device cavity and the aerosol-generating article received therein.

[0297] In such an airtight configuration, there will be substantially no gaps or empty spaces between the peripheral walls defining the device cavity and the aerosol-generating article for air to flow therethrough.

[0298] A tight fit with the aerosol-generating article may be established along the entire length of the device cavity or along a portion of the length of the device cavity.

[0299] The aerosol generating device includes an airflow channel extending between a channel inlet and a channel outlet. The airflow channel may be configured to establish fluid communication between an interior of the device cavity and an exterior of the aerosol generating device. The airflow channel of the aerosol generating device may be defined within a housing of the aerosol generating device to allow fluid communication between an interior of the device cavity and an exterior of the aerosol generating device. When an aerosol-generating article is received within the device cavity, the airflow channel may be configured to provide air flowing into the article for delivery of generated aerosol to a user who draws from a mouth end of the article.

[0300] More particularly, in the system according to the invention, the aerosol generating device comprises at a proximal end a heating chamber for at least partially receiving the aerosol generating rod to heat the aerosol generating substrate, and at a distal end the aerosol generating device comprises an opening for allowing airflow into the heating chamber along a longitudinal axis of the heating chamber, the diameter of such opening defining the above-mentioned airflow channel being smaller than the inner diameter of the annular portion.

[0301] This has the advantage that when the aerosol-generating article is fully inserted into the heating chamber, direct fluid communication is established between the exterior of the aerosol-generating device and the core portion of the aerosol-generating rod, while the distal end where the opening is formed closes the upstream end of the annular portion, so that fluid communication between the exterior of the aerosol-generating device and the annular portion is substantially restricted and air flow from the exterior of the aerosol-generating device into the annular portion is substantially prevented.

[0302] Thus, during use, any imbalance in porosity and RTD between the core portion and the annular portion is offset, and the overall RTD of the aerosol-generating article substantially corresponds to the sum of the RTD of the core portion and the RTD of the downstream section.

[0303] In use, the annular portion is blocked and the RTD of the aerosol generating system may be at least 60 millimeters H2O, preferably at least 70 millimeters H2O, more preferably at least 80 millimeters H2O.

[0304] In use, the annular portion is blocked and the RTD of the aerosol generating system may be 160 millimeters H2O or less, preferably 150 millimeters H2O or less, more preferably 140 millimeters H2O or less.

[0305] In some embodiments, in the aerosol generating device, the heater is an internal heater, such as a pin heater of a blade heater configured to be inserted into a core portion when the aerosol generating article is received in the heating chamber. The heater may be located within the device cavity or the heating chamber.

[0306] The heater may include one or more resistive heating elements. Suitable materials for forming the one or more resistive heating elements include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys, and composites made of ceramic and metallic materials. Such composites may include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, Timetal®, and iron-manganese-aluminum-based alloys.

[0307] In some embodiments, the one or more resistive heating elements include one or more stamped sections of an electrically resistive material (such as stainless steel). Alternatively, the at least one resistive heating element may include a heating wire or filament (e.g., Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wire).

[0308] In some embodiments, the heater includes an electrically insulating substrate, and one or more resistive heating elements are provided on the electrically insulating substrate.

[0309] The electrically insulating substrate may comprise any suitable material. For example, the electrically insulating substrate may comprise one or more of paper, glass, ceramic, anodized metal, coated metal, and polyimide. The ceramic may comprise mica, alumina (Al2O3), or zirconia (ZrO2). The electrically insulating substrate preferably has a thermal conductivity of about 40 watts per meter Kelvin or less, preferably about 20 watts per meter Kelvin or less, and ideally about 2 watts per meter Kelvin or less.

[0310] The heater may comprise a heating element comprising a rigid, electrically insulating substrate having one or more conductive tracks or wires arranged on its surface. The size and shape of the electrically insulating substrate may allow the heater to be inserted directly into the aerosol-generating substrate. If the electrically insulating substrate is not sufficiently rigid, the heating element may comprise further reinforcing means. An electric current may be passed through the one or more conductive tracks to heat the heating element and the aerosol-generating substrate.

[0311] In other embodiments, the aerosol-generating article comprises a susceptor element embedded within the core portion and adapted to heat the aerosol-generating substrate, as described above. In these embodiments, the heater in the aerosol-generating device may include an induction heating arrangement. The induction heating arrangement may comprise an inductor coil and a power source configured to provide a high-frequency oscillating current to the inductor coil. As used herein, high-frequency oscillating current means an oscillating current having a frequency of about 500 kHz to about 30 MHz. The heater may advantageously comprise a DC / AC inverter for converting a DC current provided by a DC power source to an alternating current. The inductor coil may be arranged to generate a high-frequency oscillating electromagnetic field upon receiving the high-frequency oscillating current from the power source. The inductor coil may be arranged to generate a high-frequency oscillating electromagnetic field within the device cavity. In some embodiments, the inductor coil may substantially surround the device cavity. The inductor coil may extend at least partially along the length of the device cavity.

[0312] In use, the heater can be controlled to operate within a defined operating temperature range that is less than the maximum operating temperature. The operating temperature range within the heating chamber (or device cavity) is preferably from about 150 degrees Celsius to about 300 degrees Celsius. The operating temperature range of the heater may be from about 150 degrees Celsius to about 250 degrees Celsius.

[0313] Preferably, the operating temperature range of the heater may be between about 150 degrees Celsius and about 200 degrees Celsius. More preferably, the operating temperature range of the heater may be between about 180 degrees Celsius and about 200 degrees Celsius.

[0314] The aerosol generating device may include a power source. The power source may be a DC power source. In some embodiments, the power source is a battery. The power source may be a nickel metal hydride battery, a nickel cadmium battery, or a lithium-based battery (e.g., lithium cobalt, lithium iron phosphate, or lithium polymer battery). However, in some embodiments, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may have a capacity that allows for the storage of sufficient energy for one or more user operations, such as one or more aerosol generating experiences. For example, the power source may have a capacity sufficient to allow continuous heating of the aerosol-generating substrate for approximately six minutes, or a multiple of six minutes, corresponding to the typical time it takes to smoke one conventional cigarette. In another example, the power source may have a capacity sufficient to allow for a predetermined number of puffs, or for discontinuous activation of the heater.

[0315] [Example] The following provides a non-exhaustive list of non-limiting examples, any one or more of the features of which may be combined with any one or more features of the other examples, embodiments, or aspects described herein.

[0316] Example 1. 1. An aerosol-generating article comprising: an aerosol-generating rod extending from an upstream end to a downstream end; and a downstream section provided downstream of the aerosol-generating rod and abutting the downstream end of the aerosol-generating rod, wherein the aerosol-generating rod includes a substantially cylindrical core portion having a longitudinal axis and an annular portion surrounding the core portion and extending coaxially with the core portion, the annular portion being air permeable such that an upstream end of the annular portion within is in fluid communication with the downstream section. Example 2. 10. An aerosol-generating article according to Example 1, wherein the core portion comprises an aerosol-generating substrate and has an average porosity of 0.15 to 0.45. Example 3. An aerosol-generating article according to example 1 or 3, wherein the average porosity of the annular portion is at least 120 percent of the average porosity of the core portion. Example 4. An aerosol-generating article according to any of Examples 1-3, wherein the downstream section comprises a hollow tubular element, the hollow tubular element defining an internal cavity and abutting the downstream end of the aerosol-generating rod. Example 5. An aerosol-generating article according to example 4, wherein the inner diameter of the annular portion is smaller than the inner diameter of the hollow tubular element. Example 6. An aerosol-generating article according to example 4 or 5, wherein the downstream section comprises a mouthpiece element downstream of the hollow tubular element, and the article further comprises a wrapper surrounding the aerosol-generating rod, the hollow tubular element, and the mouthpiece. Example 7. An aerosol-generating article according to any one of Examples 4 to 6, comprising a ventilation zone at a location along the hollow tubular element. Example 8. An aerosol-generating article according to any one of Examples 1 to 7, wherein the annular portion comprises straight, axially oriented fibers. Example 9. The aerosol-generating article according to example 8, wherein the fibers are selected from cellulose acetate fibers, polylactic acid (PLA) fibers, polypropylene fibers, poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHVB) fibers, rayon fibers, viscose fibers, regenerated cellulose fibers, and combinations thereof. Example 10. An aerosol-generating article according to example 8 or 9, wherein the annular portion comprises two or more longitudinal segments of tow material, and the tow material of adjacent ones of the two or more longitudinal segments are joined together at least along the longitudinal ends of the segments to form an integral annular portion. Example 11. 11. The aerosol-generating article according to any one of Examples 8 to 10, wherein the fibers have a denier per filament (dpf) of 3.0 dpf to 15.0 dpf. Example 12. 12. The aerosol-generating article according to claim 11, wherein the fibers have a dpf of between 5.0 dpf and 10.0 dpf. Example 13. An aerosol-generating article according to any one of Examples 8 to 12, wherein the fibres have a Y-shaped cross section. Example 14. An aerosol-generating article according to any one of Examples 1 to 13, wherein the core portion has a cross-sectional porosity of 0.15 to 0.30. Example 15. An aerosol-generating article according to any one of Examples 1 to 14, wherein the core portion has a cross-sectional porosity distribution of 0.04 to 0.22. Example 16. An aerosol-generating article according to any one of Examples 1 to 15, wherein the annular portion has a cross-sectional porosity of 0.3 to 0.95. Example 17. An aerosol-generating article according to any one of Examples 1 to 16, comprising a susceptor element disposed within the core portion and thermally coupled to the aerosol-generating substrate. Example 18. An aerosol-generating article according to any one of Examples 1 to 17, wherein the length of the aerosol-generating rod is between 10 mm and 35 mm. Example 19. An aerosol-generating article according to any one of Examples 1 to 18, wherein the length of the hollow tubular element is between 10 millimeters and 35 millimeters. Example 20. An aerosol-generating article according to any one of Examples 1 to 19, wherein the outer diameter of the article is between 4 millimeters and 10 millimeters. Example 21. An aerosol-generating article according to any one of Examples 1 to 20, wherein the annular portion radially abuts the core portion. Example 22. An aerosol-generating article according to any one of Examples 1 to 21, wherein the outer diameter of the core portion is between 3 mm and 7 mm. Example 23. An aerosol-generating article according to any one of Examples 1 to 22, wherein the outer diameter of the core portion is between 3.5 mm and 5.75 mm. Example 24. An aerosol-generating article according to any one of Examples 1 to 23, wherein the overall length of the article is between 25 millimeters and 108 millimeters. Example 25. An aerosol-generating article according to any one of Examples 1 to 24, wherein the overall length of the article is between 40 mm and 70 mm. Example 26. The aerosol-generating article according to any one of Examples 1 to 25, wherein the RTD of the annular portion is between 10 millimeters HO and 65 millimeters HO. Example 27. An aerosol-generating article according to any one of Examples 1 to 26, wherein the RTD of the annular portion is between 30 millimeters HO and 60 millimeters HO. Example 28. An aerosol generating system comprising an aerosol generating article according to any one of Examples 1 to 27 and an aerosol generating device including a heating chamber opening at a proximal end for at least partially receiving an aerosol generating rod and heating an aerosol generating substrate, the aerosol generating device including an opening at a distal end allowing airflow to enter the heating chamber along a longitudinal axis of the heating chamber, the diameter of the opening being smaller than the inner diameter of the annular portion. Example 29. An aerosol generating system according to Example 28, wherein when the aerosol-generating article is received within the heating chamber and an upstream end of the aerosol-generating article abuts the distal end of the heating chamber, the RTD of the system is between 60 millimeters HO and 160 millimeters HO.

[0317] The invention will now be further described with reference to the drawings of the accompanying drawings, in which:

[0318] The aerosol-generating article 10 shown in Figure 1 comprises an aerosol-generating rod 12 and a downstream section 14 located downstream of the aerosol-generating rod 12. The aerosol-generating article 10 thus extends from an upstream or distal end 16, which is substantially coincident with the upstream end of the aerosol-generating rod 12, to a downstream or oral end 18, which is coincident with the downstream end of the downstream section 14. The downstream section 14 includes a hollow tubular element 30 and a mouthpiece element 50. A wrapper 24 surrounds the aerosol-generating rod 12, the hollow tubular element 30, and the mouthpiece element 50.

[0319] The aerosol-generating article 10 has an overall length of about 45 millimeters and an outer diameter of about 7.7 mm.

[0320] The aerosol-generating rod has a length of 11 millimeters. The aerosol-generating rod includes a core portion 20 comprising shredded tobacco material. More specifically, the core portion 20 includes homogenized tobacco material in the form of a sheet assembled into a cylindrical shape, the homogenized tobacco material including 13 percent to 16 percent glycerin by weight. The average porosity of the core portion is about 0.3. The aerosol-generating article 10 further includes an elongated susceptor element 22 in the form of a plate embedded within the aerosol-generating substrate within the core portion 20 and thermally coupled to the aerosol-generating substrate.

[0321] The aerosol-generating rod further includes an annular portion 24 that surrounds and radially abuts the core portion 20. Thus, as shown in Figure 2, the inner diameter of the annular portion 24 substantially matches the outer diameter of the core portion.

[0322] The average porosity of the annular portion is 0.6. The annular portion is formed of a plurality of straight, axially oriented fibers of cellulose acetate.

[0323] The hollow tubular element 30 has a length of about 12 millimeters, an outer diameter of about 7.7 millimeters, and an inner diameter of about 5.5 millimeters. The peripheral wall thickness of the hollow tubular element 30 is therefore about 1.1 millimeters.

[0324] The hollow tubular element 30 defines an interior cavity 32 that extends entirely from the upstream end of the hollow tubular element 30 to the downstream end of the hollow tubular element 30. The interior cavity 32 is substantially empty, thereby allowing substantially unrestricted airflow therealong. The hollow tubular element 30 does not substantially contribute to the overall RTD of the aerosol-generating article 10.

[0325] The inner diameter of hollow tubular element 30 is greater than the inner diameter of annular portion 22 such that annular portion 22 is in direct fluid communication with interior cavity 32 .

[0326] The aerosol-generating article 10 includes a ventilation zone 40 provided at a location along the hollow tubular element 30. More specifically, the ventilation zone 40 is provided approximately 26 millimeters from the downstream end of the article 10. The ventilation zone 40 is provided 4 mm upstream from the upstream end of the mouthpiece element 50. The ventilation zone 40 includes a circumferential row of openings or perforations surrounding the hollow tubular element 30. The perforations of the ventilation zone 40 extend through the wall of the hollow tubular element 30 to permit ingress of fluid from the exterior of the article 10 into the interior cavity 32. The ventilation level of the aerosol-generating article 10 is approximately 16 percent.

[0327] The mouthpiece element 50 extends from the downstream end of the hollow tubular element 30 to the downstream or mouth end of the aerosol-generating article 10. The mouthpiece element 50 has a length of about 22 mm. The outer diameter of the mouthpiece element 50 is about 7.7 mm. The mouthpiece element 50 comprises a low density cellulose acetate filter segment. The RTD of the mouthpiece element 50 is about 8 mmH2O. The mouthpiece element 50 may be individually wrapped with a plug wrap (not shown).

[0328] The aerosol-generating article further comprises an elongated susceptor 60 in the form of a rectangular strip provided within the core portion 20 .

[0329] Figure 3 illustrates an aerosol generation system 100 comprising an exemplary aerosol generation device 1 and an aerosol-generating article 10 equivalent to that shown in Figures 1 and 2. In particular, Figure 3 illustrates a downstream mouth end portion of the aerosol generation device 1 in which a device cavity is defined and which can receive the aerosol-generating article 10.

[0330] The aerosol generating device 1 comprises a housing (or body) 4. The housing 4 includes a peripheral wall 6 and an end wall 8. The peripheral wall 6 defines a device cavity for receiving an aerosol-generating article 10. The device cavity is defined by a closed distal end and an open oral end. The oral end of the device cavity is located at the oral end of the aerosol generating device 1. The aerosol-generating article 10 is configured to be received through the oral end of the device cavity and configured to abut the closed end of the device cavity.

[0331] A device airflow inlet 5 is defined in the end wall 8. Air may enter the core portion 20 through the device airflow inlet 5, as illustrated by the dotted arrow in Figure 3. At the same time, the end wall 8 effectively blocks the end face of the annular portion, since the diameter of the device airflow inlet 5 is smaller than the outer diameter of the core portion 20. In this manner, fluid communication is selectively established between the exterior of the aerosol generation device 1 and the aerosol-generating substrate within the core portion 20, while airflow into the annular portion is restricted.

[0332] The aerosol generating device 1 further comprises a heating element in the form of an inductor coil 7 adapted to induce an electric current in the susceptor element 24. The aerosol generating device 1 further comprises a power supply (not shown) for supplying power to the heater. A controller (not shown) is also provided for controlling such power supply to the heater. The heater is configured to controllably heat the aerosol-generating article 10, during use, when the aerosol-generating article 1 is received within the device 1.

[0333] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like, should be understood in all instances as modified by the term "about." Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A±10 percent. Within this context, the number A may be considered to include a numerical value that is within the general standard error for the measurement of the property that the number A modifies. The number A may deviate by the percentages recited above, in some cases as used in the appended claims, provided that the amount by which A deviates does not materially affect the basic and novel properties of the claimed invention. Also, all ranges include the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. An aerosol-generating article comprising: an aerosol-generating rod extending from an upstream end to a downstream end; a downstream section provided downstream of the aerosol generation rod and abutting the downstream end of the aerosol generation rod, the aerosol-generating rod includes a substantially cylindrical core portion having a longitudinal axis and an annular portion surrounding the core portion and extending coaxially with the core portion; the annular portion is air permeable such that an upstream end of the annular portion therein is in fluid communication with the downstream section; the core portion comprises an aerosol-generating substrate and has a cross-sectional porosity of 0.10 to 0.45, the cross-sectional porosity of the annular portion being at least 120 percent of the cross-sectional porosity of the core portion; An aerosol-generating article wherein the annular portion has a thickness of at least 0.5 millimeters.

2. 2. The aerosol-generating article of claim 1, wherein the downstream section comprises a hollow tubular element defining an interior cavity and abutting the downstream end of the aerosol-generating rod.

3. 3. The aerosol-generating article of claim 2, wherein the inner diameter of the annular portion is smaller than the inner diameter of the hollow tubular element.

4. 4. The aerosol-generating article of claim 2 or 3, wherein the downstream section includes a mouthpiece element downstream of the hollow tubular element, and the article further comprises a wrapper surrounding the aerosol-generating rod, the hollow tubular element, and the mouthpiece.

5. 4. The aerosol-generating article of claim 2 or 3, comprising ventilation zones at locations along the hollow tubular element.

6. 3. The aerosol-generating article of claim 1, wherein the annular portion comprises straight, axially oriented fibers.

7. 7. The aerosol-generating article of claim 6, wherein the fibers are selected from cellulose acetate fibers, polylactic acid (PLA) fibers, polypropylene fibers, poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHVB) fibers, rayon fibers, viscose fibers, regenerated cellulose fibers, and combinations thereof.

8. 7. The aerosol-generating article of claim 6, wherein the annular portion comprises two or more longitudinal segments of tow material, and the tow material of adjacent ones of the two or more longitudinal segments is joined together at least along the longitudinal edges of the segments to form an integral annular portion.

9. 7. The aerosol-generating article of claim 6, wherein the fibers have a denier per filament (dpf) of from 3.0 dpf to 15.0 dpf.

10. 3. The aerosol-generating article according to claim 1, wherein the core portion has a cross-sectional porosity of 0.15 to 0.

30.

11. 3. The aerosol-generating article according to claim 1, wherein the core portion has a cross-sectional porosity distribution of 0.04 to 0.

22.

12. 3. The aerosol-generating article according to claim 1, wherein the annular portion has a cross-sectional porosity of 0.3 to 0.

95.

13. 3. The aerosol-generating article according to claim 1, further comprising a susceptor element disposed within the core portion and thermally coupled to the aerosol-generating substrate.

14. 3. The aerosol-generating article of claim 1, wherein the annular portion radially abuts the core portion.

15. 3. An aerosol generation system comprising: an aerosol-generating article according to claim 1 or 2; and an aerosol generating device including, at a proximal end, a heating chamber opening for at least partially receiving the aerosol-generating rod and heating the aerosol-generating substrate, the aerosol generating device including, at a distal end, an opening for allowing airflow into the heating chamber along a longitudinal axis of the heating chamber, the diameter of the opening being smaller than the inner diameter of the annular portion.

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