Aerosol-generating article with ventilated hollow section

Abstract

An aerosol-generating article (10) for generating an inhalable aerosol upon heating, the aerosol-generating article comprising: a rod (12) of an aerosol-generating substrate; a mouthpiece section (18) comprising a plug of filter material and arranged downstream of and longitudinally aligned with the rod (12); and a hollow tubular section (16) between the rod (12) and the mouthpiece section (18). The hollow tube section (16) is longitudinally aligned with the rod (12) and the mouthpiece section (18) and defines a cavity extending up to an upstream end of the mouthpiece section (18). The article (10) also includes a ventilation zone (26) located at a location along the hollow tubular section. The hollow tubular section (16) has an equivalent inner diameter of at least about 5 mm at the location of the ventilation zone (26). The rod (12) of the aerosol-generating substrate includes at least one aerosol former, the rod (12) having an aerosol former content of at least about 10% by dry weight.

Description

[0001] This application is a divisional application of the invention patent application with the title "Aerosol-generating article having a ventilated hollow section", an international filing date of December 20, 2019, an international application number of PCT / EP2019 / 086801, and a national application number of 201980081151.5. Technical Field

[0002] The present invention relates to an aerosol-generating article comprising an aerosol-generating substrate and adapted to generate an inhalable aerosol upon heating. Background Art

[0003] Aerosol-generating articles are known in the art, in which an aerosol-generating substrate (such as a tobacco-containing substrate) in the aerosol-generating article is heated rather than burned. Generally, in such heated smoking articles, an aerosol is generated by transferring heat from a heat source to a physically separated aerosol-generating substrate or material, which may be positioned in contact with, inside, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in the air drawn through the aerosol-generating article. As the released compounds cool, the compounds condense to form an aerosol.

[0004] Many prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol-generating devices, in which an aerosol is generated by transferring heat from one or more electrical heater elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article.

[0005] In the past, fragments, shreds or strips of randomly oriented tobacco material were typically used to produce the substrate for a heated aerosol-generating article. As an alternative, International Patent Application WO-A-2012 / 164009 proposes a rod of a heated aerosol-generating article formed from a sheet of aggregated tobacco material. The rod disclosed in WO-A-2012 / 164009 has longitudinal porosity that allows air to be drawn through the rod. Effectively, creases in the sheet of aggregated tobacco material define longitudinal channels through the rod.

[0006] Alternative rods for heat-generating aerosol-generating articles are known from international patent application WO-A-2011 / 101164. These rods are formed from strips of homogenized tobacco material, which can be formed by casting, rolling, calendering or extruding a mixture comprising particulate tobacco and at least one aerosol-forming agent to form a sheet of homogenized tobacco material. In an alternative embodiment, the rods of WO-A-2011 / 101164 can also be formed from strips of homogenized tobacco material, which are obtained by extruding a mixture comprising particulate tobacco and at least one aerosol-forming agent to form a continuous length of homogenized tobacco material.

[0007] The substrate for a heat-generating aerosol-generating article typically further comprises an aerosol-forming agent, i.e. a compound or mixture of compounds that promotes the formation of an aerosol during use and preferably substantially resists thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-forming agents include: polyols such as propylene glycol, triethylene glycol, 1,3-butanediol, glycerol; esters of polyols such as glycerol monoacetate, glycerol diacetate or glycerol triacetate; and fatty acid esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

[0008] It is also common for an aerosol-generating article for generating an inhalable aerosol upon heating to include one or more additional elements, which are assembled with the substrate in the same packaging material. Examples of such additional elements include a mouthpiece filter section, a support element adapted to impart structural strength to the aerosol-generating article, a cooling element adapted to cool the aerosol before it reaches the mouthpiece, etc. However, although the inclusion of such additional elements has been proposed in view of their beneficial effects, this generally complicates the overall structure of the aerosol-generating article and makes its manufacture more complex and expensive. In fact, the manufacture of such multi-component aerosol-generating articles typically requires rather complex manufacturing machinery and assembly machinery.

[0009] In view of this, aerosol-generating articles with a simpler structure have also been proposed. However, in the absence of certain additional components, such as for example an aerosol cooling element, it may become more difficult to manufacture an aerosol-generating article that consistently provides a satisfactory aerosol delivery and RTD to the consumer. Summary of the Invention

[0010] Accordingly, there is a desire to provide an aerosol-generating article that can provide a consistently satisfactory aerosol delivery to a consumer during use. Additionally, there is a desire to provide such an improved aerosol-generating article having a satisfactory RTD value. There is also a desire to provide such an aerosol-generating article that can be manufactured efficiently and at high speed, preferably having a low RTD variability between one article and another. The present invention aims to provide a technical solution suitable for achieving at least one of the above desired results.

[0011] According to one aspect of the present invention, there is provided an aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising:

[0012] a rod of an aerosol-generating substrate; a mouthpiece section of a plug comprising a filter material, the mouthpiece section being disposed downstream of the rod and longitudinally aligned with the first section; and a hollow tubular section at a position between the rod and the mouthpiece section. The hollow tube section is longitudinally aligned with the rod and the mouthpiece section. Additionally, the hollow tubular section defines a cavity that extends all the way to the upstream end of the mouthpiece section. The aerosol-generating article further comprises a ventilation zone at a position along the hollow tubular section. The equivalent inner diameter of the hollow tubular section at the position of the ventilation zone can be at least about 5 millimeters. The rod of the aerosol-generating substrate comprises at least one aerosol-forming agent, and the rod of the aerosol-generating substrate has an aerosol-forming agent content of at least about 10% by dry weight.

[0013] The term "aerosol-generating article" is used herein to denote 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" denotes a substrate capable of releasing volatile compounds upon heating to generate an aerosol.

[0014] Conventional smoking is ignited when a user applies a flame to one end of a cigarette and draws air through the other end. The local heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to be ignited, and the resulting combustion produces inhalable smoke. In contrast, in a heated aerosol-generating article, an aerosol is generated by heating a flavor-generating substrate such as tobacco. Heated aerosol-generating articles are known to include, for example, electrically heated aerosol-generating articles, and aerosol-generating articles in which an aerosol is generated by heat transfer from a combustible fuel element or heat source to a physically separate aerosol-forming material. For example, the aerosol-generating article according to the present invention finds a particular application in aerosol-generating systems that include an electrically heated aerosol-generating device having an internal heater blade adapted to be inserted into the rod of the aerosol-generating substrate. This type of aerosol-generating article is described in the prior art (for example, in European Patent Application EP 0822670).

[0015] As used herein, the term "aerosol generating device" refers to a device including a heater element that interacts with an aerosol-forming substrate of an aerosol-forming article to generate an aerosol.

[0016] In the present specification, the term "tubular section" is used to denote an elongate element that defines a lumen or an airflow passage along its longitudinal axis. In particular, the term "tubular" will hereinafter be used to refer to a tubular element having a substantially cylindrical cross-section and defining at least one airflow conduit that establishes unbroken fluid communication between an upstream end and a downstream end of the tubular element. However, it should be understood that alternative geometries of the cross-section of the tubular element are possible.

[0017] As used herein, the term "longitudinal" refers to the direction corresponding to the main longitudinal axis of the aerosol-forming article, which extends between an upstream end and a downstream end of the aerosol-forming article. As used herein, the terms "upstream" and "downstream" describe the relative positions of elements or portions of elements of the aerosol-forming article with respect to the direction in which aerosol is delivered through the aerosol-forming article during use.

[0018] During use, air is drawn through the aerosol-forming article in the longitudinal direction. The term "transverse" refers to a direction perpendicular to the longitudinal axis. Unless otherwise specified, any reference to a "cross-section" of the aerosol-forming article or a component of the aerosol-forming article refers to a transverse cross-section.

[0019] The term "length" denotes the dimension of a component of the aerosol-forming article in the longitudinal direction. For example, it can be used to denote the dimension of a rod or an elongate tubular element in the longitudinal direction.

[0020] The term "thickness of the peripheral wall of the tubular element" is used in the present specification to denote the minimum distance measured between an outer surface and an inner surface of the wall that bounds the tubular element at its perimeter. In practice, the distance at a given location is measured along a direction that is locally substantially perpendicular to the outer and inner surfaces of the tubular element. For a tubular element having a substantially circular cross-section, this distance is measured along a substantially radial direction of the tubular element.

[0021] In some embodiments, the thickness of the peripheral wall of the tubular element is constant. In alternative embodiments, the thickness of the peripheral wall of the tubular element varies along the length of the tubular element. This may be because the tubular element is formed from a material having an irregular surface finish (e.g., the tubular element is provided in the form of a cellulose acetate tube). Alternatively, this may be because the tubular element is designed to include tapered portions and the like. In embodiments where the thickness of the peripheral wall of the tubular element varies along the length of the tubular element, the "thickness of the peripheral wall of the tubular element" is considered to be an average value calculated based on a number of values measured as the minimum distance between the outer surface and the inner surface of the wall at different positions along the length of the tubular element.

[0022] In any embodiment, a particularly important parameter is the thickness of the peripheral wall of the tubular element at the location of the ventilation zone.

[0023] The expression "air-impermeable material" is used throughout this specification to mean a material that does not allow fluids, especially air and smoke, to pass through voids or pores in the material. If the hollow tubular section is formed from a material that is air-impermeable and aerosol particle-impermeable, then the air and aerosol particles drawn through the hollow tubular section are forced to flow through the air flow conduit defined inside the hollow tubular section, but cannot flow through the peripheral wall of the hollow tubular section.

[0024] As used in this specification, the term "homogenized tobacco material" encompasses any tobacco material formed by the coalescence of tobacco material particles. A sheet or web of homogenized tobacco material is formed by coalescing particulate tobacco obtained by grinding or otherwise powdering one or both of tobacco leaves and tobacco stems. Additionally, the homogenized tobacco material may include small amounts of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the processing, handling, and transportation of tobacco. Sheets of homogenized tobacco material can be produced by casting, extrusion, papermaking processes, or any other suitable process known in the art.

[0025] The term "porous" is used herein to refer to a material that provides a plurality of holes or openings that allow air to pass through the material.

[0026] Throughout this specification, the term "ventilation level" is used to represent the volume ratio of the air flow entering the aerosol-generating article via the ventilation zone (ventilation air flow) to the sum of the aerosol air flow and the ventilation air flow. The greater the ventilation level, the higher the dilution of the aerosol stream delivered to the consumer.

[0027] As briefly described above, the aerosol-generating article of the present invention includes a stem of an aerosol-generating substrate; a mouthpiece section including a plug of filter material; and a hollow tubular section at a position between the stem and the mouthpiece section. All three elements are longitudinally aligned. The stem of the aerosol-generating substrate includes at least one aerosol-forming agent.

[0028] Compared with known aerosol-generating articles, the rod of the aerosol-generating substrate has an aerosol-forming agent content of at least about 10% by dry weight. In addition, the hollow tubular section defines a cavity that extends all the way to the upstream end of the mouthpiece section, and ventilation zones are provided at positions along the hollow tubular section. Additionally, the equivalent inner diameter of the hollow tubular section is at least about 5 millimeters.

[0029] By providing an aerosol-generating article in which a hollow tubular element is arranged between the rod of the aerosol-generating substrate and the mouthpiece, and in which the hollow tubular element defines a cavity that extends all the way to the upstream end of the mouthpiece section, the overall structural complexity of the article can be significantly reduced compared to existing aerosol-generating articles. This advantageously simplifies the manufacturing process and reduces the complexity of the manufacturing and assembly equipment required to implement the manufacturing process.

[0030] One such aerosol-generating article does not have to include an aerosol cooling element adapted to reduce the temperature of the aerosol stream drawn through the aerosol-generating article - for example, as is the case with the aerosol-generating article described in international patent application WO 2013 / 120565.

[0031] The inventors have found that satisfactory cooling of the aerosol stream generated upon heating the article and drawn through the hollow tubular element is achieved by providing ventilation zones at positions along the hollow tubular section. Additionally, the inventors have surprisingly found that by using a hollow tubular section having an equivalent inner diameter of at least about 5 millimeters, the increased aerosol dilution caused by introducing ventilation air into the article can be counteracted.

[0032] Without wishing to be bound by theory, it is assumed that since the temperature of the aerosol stream rapidly decreases upon introduction of ventilation air as the aerosol moves towards the mouthpiece section, and the ventilation air enters the aerosol stream at a position relatively close to the upstream end of the hollow tubular section (i.e., sufficiently close to the heat source and the rod of the aerosol-generating substrate), significant cooling of the aerosol stream is achieved, which has a beneficial effect on the condensation and nucleation of aerosol particles. Thus, the overall ratio of the aerosol particulate phase to the aerosol gas phase can be increased compared to existing non-ventilated aerosol-generating articles.

[0033] At the same time, by using a hollow tubular element with an equivalent inner diameter of 5 millimeters or greater, the total internal volume of the hollow tubular element (where the aerosol nucleation process begins once the aerosol components leave the rod of the aerosol-forming substrate) and the cross-sectional surface area of the hollow tubular section are effectively maximized, while ensuring that the hollow tubular section has the necessary structural strength to prevent collapse of the aerosol-generating article and to provide some support for the rod of the aerosol-forming substrate, and minimizing the RTD of the hollow tubular section. The larger value of the cross-sectional surface area of the cavity of the hollow tubular section is associated with a reduced velocity of the aerosol flow traveling along the aerosol-generating article, which is understood to be beneficial for aerosol nucleation. In fact, without wishing to be bound by theory, by providing a cavity with a large volume as in the case of the articles of the present invention, a cooling chamber is effectively provided in which, due to enhancing the nucleation phenomenon by slowing down the flow of the aerosol stream, condensation of aerosol particles upstream of the mouth end of the article is favored.

[0034] Providing a sufficiently wide tubular cavity downstream of the rod of the aerosol-forming substrate is understood to be beneficial for forming a satisfactory amount of aerosol during use. Subsequently, a larger portion of the generated aerosol particles begins to condense before reaching the mouth end of the article.

[0035] In fact, the inventors have surprisingly found that the beneficial effect of enhanced nucleation can significantly offset the less desirable effect of dilution, such that aerosol-generating articles according to the present invention consistently achieve satisfactory aerosol delivery values. This is particularly advantageous for "short" aerosol-generating articles, such as those in which the length of the rod of the aerosol-forming substrate is less than about 40 millimeters, preferably less than 25 millimeters, even more preferably less than 20 millimeters, or in which the total length of the aerosol-generating article is less than about 70 millimeters, preferably less than about 60 millimeters, even more preferably less than 50 millimeters. As will be understood, in such aerosol-generating articles, there is little time and space for aerosol formation and the particulate phase of the aerosol to become available for delivery to the consumer.

[0036] Furthermore, since the hollow tubular element contributes substantially nothing to the RTD of the aerosol-generating article, in the aerosol-generating articles according to the present invention, the total RTD of the article can be finely tuned powerfully by adjusting the length and density of the rod of the aerosol-forming substrate or the length and density of the filter material section of the mouthpiece. This enables the consistent and highly accurate manufacture of aerosol-forming substrates with a predetermined RTD, thereby providing a satisfactory level of RTD for the consumer even in the presence of ventilation.

[0037] The aerosol-generating articles according to the present invention can be made in a continuous process, which can be carried out efficiently at high speed and can be conveniently manufactured on existing production lines for heated aerosol-generating articles without the need for substantial modification of the manufacturing equipment.

[0038] The outer diameter of the rod of the aerosol - generating substrate is preferably approximately equal to the outer diameter of the aerosol - generating article.

[0039] Preferably, the rod of the aerosol - generating substrate has an outer diameter of at least 5 millimeters. The rod of the aerosol - generating substrate can have an outer diameter between about 5 millimeters and about 12 millimeters, such as between about 5 millimeters and about 10 millimeters or between about 6 millimeters and about 8 millimeters. In a preferred embodiment, the rod of the aerosol - generating substrate has an outer diameter within 10% of 7.2 millimeters.

[0040] The rod of the aerosol - generating substrate can have a length between about 5 millimeters and about 100 millimeters. Preferably, the rod of the aerosol - generating substrate has a length of at least about 5 millimeters, more preferably at least about 7 millimeters. Additionally, or alternatively, the rod of the aerosol - generating substrate preferably has a length less than about 80 millimeters, more preferably less than about 65 millimeters, even more preferably less than about 50 millimeters. In a particularly preferred embodiment, the rod of the aerosol - generating substrate preferably has a length less than about 35 millimeters, more preferably less than about 25 millimeters, even more preferably less than about 20 millimeters. In one embodiment, the rod of the aerosol - generating substrate can have a length of about 10 millimeters. In a preferred embodiment, the rod of the aerosol - generating substrate has a length of about 12 millimeters.

[0041] Preferably, the rod of the aerosol - generating substrate has a substantially uniform cross - section along the length of the rod. Particularly preferably, the rod of the aerosol - generating substrate has a substantially circular cross - section.

[0042] In a preferred embodiment, the aerosol - forming substrate comprises one or more sheets of aggregated homogenized tobacco material. Preferably, one or more of the sheets of homogenized tobacco material are textured. As used herein, the term "textured sheet" means a sheet that has been wrinkled, embossed, debossed, perforated, or otherwise deformed. The textured sheets of homogenized tobacco material for use in the present invention can include a plurality of spaced - apart indentations, protrusions, perforations, or combinations thereof. According to a particularly preferred embodiment of the present invention, the rod of the aerosol - generating substrate comprises a coiled sheet of aggregated homogenized tobacco material wrapped in a packaging material.

[0043] As used herein, the term 'crimped sheet' is intended to be substantially synonymous with the term 'corrugated sheet' and denotes a sheet having a plurality of substantially parallel ridges or corrugations. Preferably, the crimped sheet of homogenized tobacco material has a plurality of ridges or corrugations that are substantially parallel to the cylindrical axis of the rod according to the invention. This advantageously aids in the aggregation of the crimped sheet of homogenized tobacco material to form a rod. However, it should be understood that the crimped sheet of homogenized tobacco material for use in the present invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that are disposed at an acute or obtuse angle to the cylindrical axis of the rod. The sheet of homogenized tobacco material for the rod of the article of the present invention may be substantially uniformly textured over substantially its entire surface. For example, the crimped sheet of homogenized tobacco material for manufacturing the rod of the aerosol-generating article according to the invention may include a plurality of substantially parallel ridges or corrugations that are substantially uniformly spaced over the width of the sheet.

[0044] The sheet or web of homogenized tobacco material for use in the present invention may have a tobacco content of at least about 40% by weight, more preferably at least about 60% by weight, more preferably at least about 70% by weight, and most preferably at least about 90% by weight on a dry weight basis.

[0045] The sheet or web of homogenized tobacco material for use in an aerosol-generating substrate may comprise one or more inherent binders (i.e., tobacco endogenous binders), one or more non-inherent binders (i.e., tobacco exogenous binders), or a combination thereof to aid in the coalescence of particulate tobacco. Alternatively or additionally, the sheet of homogenized tobacco material for use in an aerosol-generating substrate may comprise other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorants, fillers, aqueous solvents and non-aqueous solvents, and combinations thereof.

[0046] Suitable external binders included in the sheet or web of homogenized tobacco material for use in an aerosol-generating substrate are known in the art and include, but are not limited to: gums such as guar gum, xanthan gum, gum arabic, and locust bean gum; cellulose binders such as hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, and ethyl cellulose; polysaccharides such as starch; organic acids such as alginic acid; conjugate base salts of organic acids such as sodium alginate, agar, and pectin; and combinations thereof.

[0047] Suitable non-tobacco fibers included in a sheet or web of homogenized tobacco material for use in an aerosol-generating substrate are known in the art and include, but are not limited to: cellulose fibers; cork fibers; hardwood fibers; jute fibers and combinations thereof. Prior to inclusion in a sheet of homogenized tobacco material for use in an aerosol-generating substrate, the non-tobacco fibers can be processed by suitable processes known in the art, said processes including, but not limited to: mechanical pulping, refining, chemical pulping, bleaching, sulfate pulping and combinations thereof.

[0048] Preferably, the sheet or web of homogenized tobacco material comprises an aerosol former. As used herein, the term "aerosol former" describes any suitable known compound or mixture of compounds that promotes the formation of an aerosol in use and is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article.

[0049] Suitable aerosol formers are known in the art and include, but are not limited to: polyols such as propylene glycol, triethylene glycol, 1,3-butanediol, glycerol; esters of polyols such as glycerol monoacetate, glycerol diacetate or glycerol triacetate; and fatty acid esters of monocarboxylic, dicarboxylic or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

[0050] Preferred aerosol formers are polyols or mixtures thereof such as propylene glycol, triethylene glycol, 1,3-butanediol and most preferably glycerol.

[0051] The sheet or web of homogenized tobacco material may comprise a single aerosol former. Alternatively, the sheet or web of homogenized tobacco material may comprise a combination of two or more aerosol formers.

[0052] The sheet or web of homogenized tobacco material has an aerosol former content of greater than 10% by dry weight. Preferably, the sheet or web of homogenized tobacco material has an aerosol former content of greater than 12% by dry weight. More preferably, the sheet or web of homogenized tobacco material has an aerosol former content of greater than 14% by dry weight. Even more preferably, the sheet or web of homogenized tobacco material has an aerosol former content of greater than 16% by dry weight.

[0053] The sheet of homogenized tobacco material may have an aerosol former content of from about 10% to about 30% by dry weight. Preferably, the sheet or web of homogenized tobacco material has an aerosol former content of less than 25% by dry weight.

[0054] In a preferred embodiment, the sheet of homogenized tobacco material has an aerosol former content of about 20% by dry weight.

[0055] A sheet or web of homogenized tobacco for use in the aerosol-generating article of the present invention can be manufactured by methods known in the art (such as the method disclosed in International Patent Application WO-A-2012 / 164009A2). In a preferred embodiment, a sheet of homogenized tobacco material for use in an aerosol-generating article is formed from a slurry comprising particulate tobacco, guar gum, cellulose fibers, and glycerol by a casting process.

[0056] Alternative arrangements of homogenized tobacco material in a rod for use in an aerosol-generating article will be known to the person skilled in the art and may include multiple stacked sheets of homogenized tobacco material, multiple elongate tubular elements formed by winding a strip of homogenized tobacco material around its longitudinal axis, and the like.

[0057] As another alternative, the rod of the aerosol-generating substrate may comprise a non-tobacco-based nicotine-containing material, such as a sheet of absorbent non-tobacco material loaded with nicotine (e.g., in the form of a nicotine salt) and an aerosol-forming agent. Examples of such rods are described in International Application WO-A-2015 / 052652. Additionally, or alternatively, the rod of the aerosol-generating substrate may comprise non-tobacco plant material, such as aromatic non-tobacco plant material.

[0058] In the rod of the aerosol-generating substrate of the article according to the present invention, the aerosol-generating substrate is preferably wrapped by a packaging material. The packaging material may be formed from a porous or non-porous sheet material. The packaging material may be formed from any suitable material or combination of materials. Preferably, the packaging material is a paper-based packaging material.

[0059] The mouthpiece section includes a plug of filter material capable of removing particulate components, gaseous components, or combinations thereof. Suitable filter materials are known in the art and include, but are not limited to: fibrous filter materials such as, for example, cellulose acetate tow, viscose fiber, polyhydroxyalkanoate (PHA) fiber, polylactic acid (PLA) fiber, and paper; adsorbents such as, for example, activated alumina, zeolite, molecular sieve, and silica gel; and combinations thereof. Additionally, the plug of filter material may further include one or more aerosol modifiers. Suitable aerosol modifiers are known in the art and include, but are not limited to, flavorants such as, for example, menthol. In some embodiments, the mouthpiece may further include a mouth-end recess downstream of the plug of filter material. By way of example, the mouthpiece may include a hollow tube longitudinally aligned with and disposed immediately downstream of the plug of filter material, the hollow tube forming a cavity at the mouth end, the cavity being open to the external environment at the mouthpiece and the downstream end of the aerosol-generating article.

[0060] The length of the mouthpiece is preferably at least about 4 mm, more preferably at least about 6 mm, and even more preferably at least about 8 mm. Additionally, or alternatively, the length of the mouthpiece is preferably less than 25 mm, more preferably less than 20 mm, and even more preferably less than 15 mm. In some preferred embodiments, the length of the mouthpiece is from about 4 mm to about 25 mm, more preferably from about 6 mm to about 20 mm. In an exemplary embodiment, the length of the mouthpiece is about 7 mm. In an exemplary embodiment, the length of the mouthpiece is about 12 mm.

[0061] The hollow tubular section is preferably an annular tube that defines and delimits an air gap within the aerosol-generating article. In effect, the hollow tubular section provides a chamber for the accumulation and inflow of volatile aerosol components released when heating the aerosol-generating substrate. As briefly described above, this chamber extends longitudinally all the way to the upstream end of the mouthpiece. This means that no intermediate element is provided between the hollow tubular section and the mouthpiece, and when the aerosol flowing through the aerosol-generating article reaches the downstream end of the hollow tubular section, the aerosol flowing through the aerosol-generating article also effectively reaches the upstream end of the mouthpiece. More specifically, the aerosol flowing through the aerosol-generating article typically reaches the upstream end of the filter material section of the mouthpiece.

[0062] Thus, in the aerosol-generating article according to the present invention, the hollow tubular section holds the rod of the aerosol-generating substrate at a predetermined distance from the mouthpiece and provides an elongated air flow conduit for aerosol formation and flow towards the mouthpiece. During use, a thermal gradient is established along this air flow conduit. In effect, a temperature difference is provided such that the temperature of the volatile aerosol components entering the hollow tubular section at the upstream end is greater than the temperature of the volatile aerosol components leaving the hollow tubular section at the downstream end (i.e., the upstream end of the mouthpiece).

[0063] On the one hand, the hollow tubular section needs to withstand any axial compression load or bending moment that may be applied to the hollow tubular section during the manufacture of the aerosol-generating article. Additionally, the hollow tubular section needs to impart structural strength to the aerosol-generating article such that it can be easily handled by the consumer and inserted into an aerosol-generating device for use. On the other hand, it is desirable that the overall volume of the chamber defined inside the hollow tubular element be as large as possible in order to facilitate aerosol formation and enhance the delivery of the aerosol to the consumer.

[0064] To meet these requirements, as briefly described above, the equivalent inner diameter of the hollow tubular section is at least about 5 mm. The term "equivalent inner diameter" is used herein to denote the diameter of a circle having the same surface area as the cross-section of the air flow conduit defined inside the hollow tubular section. The cross-section of the air flow conduit can have any suitable shape. However, as briefly described above, a circular cross-section is preferred, i.e., the hollow tubular section is effectively a cylindrical tube. In this case, the equivalent inner diameter of the hollow tubular section coincides effectively with the inner diameter of the cylindrical tube.

[0065] More preferably, the equivalent inner diameter of the hollow tubular section is at least about 5.25 mm, and even more preferably at least about 5.5 mm. In some embodiments, the equivalent inner diameter of the hollow tubular section is at least about 6 mm or at least about 6.5 mm or at least about 7 mm.

[0066] In addition, the equivalent inner diameter of the hollow tubular section is preferably less than about 10 mm. More preferably, the equivalent inner diameter of the hollow tubular section is less than about 9.5 mm, and even more preferably less than 9 mm.

[0067] The equivalent inner diameter of the hollow tubular section is measured at the location of the ventilation zone.

[0068] In a preferred embodiment, the equivalent inner diameter of the hollow tubular section is substantially constant along the length of the hollow tubular section. In other embodiments, the equivalent inner diameter of the hollow tubular section may vary along the length of the hollow tubular section.

[0069] The inventors have surprisingly found that an aerosol-generating article according to the present invention comprising a hollow tubular section having an equivalent inner diameter within the above range can provide particularly satisfactory aerosol delivery values. Without wishing to be bound by theory, it is assumed that when an incoming stream of cooler ventilation air is received into the aerosol stream and mixed with the aerosol stream, the aerosol stream flowing along the hollow tubular section having an equivalent inner diameter falling within the above range flows at a relatively low velocity. Since the aerosol stream advances relatively slowly along the hollow tubular section, the beneficial effect of cooling on aerosol nucleation is expected to be maximized under such conditions.

[0070] Preferably, the equivalent inner diameter of the hollow tubular section is substantially constant along the length of the hollow tubular section. However, in some embodiments, the cross-sectional surface area of the hollow tubular section may vary along the length of the hollow tubular section. In such embodiments, the equivalent inner diameter is measured at the location of the ventilation zone.

[0071] In a preferred embodiment, the thickness of the peripheral wall of the hollow tubular section is less than 1.5 mm. More preferably, the thickness of the peripheral wall of the hollow tubular section is less than 1250 microns, even more preferably less than 1000 microns, and most preferably less than 900 microns. In a particularly preferred embodiment, the thickness of the peripheral wall of the hollow tubular section is less than 800 microns.

[0072] Alternatively, or as an alternative, the thickness of the peripheral wall of the hollow tubular section is at least about 100 microns. Preferably, the thickness of the peripheral wall of the hollow tubular section is at least about 200 microns.

[0073] Without wishing to be bound by theory, it seems that by using a hollow tubular section having a peripheral wall with a thickness falling within the above range, it is advantageously possible to limit or even substantially prevent the diffusion of ventilation air before it comes into contact and mixes with the aerosol stream. This is understood to further favour the nucleation phenomenon. Indeed, by providing more controlled local cooling of the stream of volatile substances drawn through the hollow tubular section, the effect of the cooling on the formation of new aerosol particles can be enhanced.

[0074] As briefly described above, the aerosol-generating article according to the invention comprises a ventilation zone at a position along the hollow tubular section. Preferably, the ventilation zone is provided at a position less than about 18 mm from the upstream end of the hollow tubular section. Preferably, the distance between the ventilation zone and the upstream end of the hollow tubular section is less than about 15 mm. Even more preferably, the distance between the ventilation zone and the upstream end of the hollow tubular section is less than about 10 mm.

[0075] Additionally, or as an alternative, the distance between the ventilation zone and the upstream end of the hollow tubular section is preferably at least 2 mm. More preferably, the distance between the ventilation zone and the upstream end of the hollow tubular section is at least about 4 mm. Even more preferably, the distance between the ventilation zone and the upstream end of the hollow tubular section is at least about 6 mm.

[0076] Preferably, the ventilation zone is provided at a position along the hollow tubular section at least 2 mm from the upstream end of the mouthpiece. Preferably, the ventilation zone is provided at a position along the hollow tubular section at least 4 mm from the upstream end of the mouthpiece. Even more preferably, the ventilation zone is provided at a position along the hollow tubular section at least 6 mm from the upstream end of the mouthpiece.

[0077] When the mixture of air and aerosol particles flowing through the aerosol-generating article reaches the ventilation zone, the external air drawn through the ventilation zone into the hollow tubular section mixes with the aerosol. This rapidly reduces the temperature of the aerosol mixture while partially diluting the mixture of air and aerosol particles. However, as will be discussed in more detail below, by providing the ventilation zone at a distance from the upstream end of the mouthpiece section falling within the above range, a cooling chamber is effectively provided immediately upstream of the mouthpiece, which advantageously contributes to the nucleation and growth of aerosol particles. Thus, at least partially counteracting the dilution effect of the ventilation air entering the hollow tubular section, which advantageously enables a satisfactory level of aerosol delivery to be provided to the consumer.

[0078] In some embodiments, the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the location of the ventilation zone is less than 4. Preferably, the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the location of the ventilation zone is less than 3.5. More preferably, the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the location of the ventilation zone is less than 3. Even more preferably, the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the location of the ventilation zone is less than 2.5.

[0079] In a particularly preferred embodiment, the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the location of the ventilation zone is less than 2, more preferably less than 1.5, and even more preferably less than 1.2.

[0080] Preferably, the ventilation zone is provided at a position along the hollow tubular section that is at least 10 millimeters downstream of the downstream end of the mouthpiece section. More preferably, the ventilation zone is provided at a position along the hollow tubular section that is at least 12 millimeters downstream of the downstream end of the mouthpiece section. Even more preferably, the ventilation zone is provided at a position along the hollow tubular section that is at least 15 millimeters downstream of the downstream end of the mouthpiece section. This is advantageous because it ensures that during use, the ventilation zone is not blocked by the consumer's lip margin.

[0081] Additionally, or as an alternative, the ventilation zone is preferably located at a position along the hollow tubular section that is less than 25 millimeters downstream of the downstream end of the mouthpiece section. More preferably, the ventilation zone is located at a position along the hollow tubular section that is less than 20 millimeters downstream of the downstream end of the mouthpiece section. This advantageously ensures that during use, when the aerosol-generating article is received in the heating chamber of an electrically heated aerosol-generating device, the ventilation zone is effectively located along the position of the hollow tubular section that protrudes outside the heating chamber, such that external cooling air can be easily drawn into the hollow tubular section.

[0082] In some preferred embodiments, the ventilation zone is provided at a position along the hollow tubular section that is about 10 millimeters to about 25 millimeters downstream of the downstream end of the mouthpiece section, more preferably about 12 millimeters to about 20 millimeters downstream of the downstream end of the mouthpiece section. In an exemplary embodiment, the ventilation zone is provided at a position 18 millimeters downstream of the downstream end of the mouthpiece section along the hollow tubular section. In another exemplary embodiment, the ventilation zone is provided at a position 13 millimeters downstream of the downstream end of the mouthpiece section along the hollow tubular section.

[0083] The aerosol-generating article can generally have a ventilation level of at least about 10%, preferably at least about 20%.

[0084] In a preferred embodiment, the aerosol - generating article has a ventilation level of at least about 30%. More preferably, the aerosol - generating article has a ventilation level of at least about 35%. Additionally, or alternatively, the aerosol - generating article preferably has a ventilation level of less than about 60%. More preferably, the aerosol - generating article has a ventilation level of less than about 50%. In a particularly preferred embodiment, the aerosol - generating article has a ventilation level of from about 30% to about 60%. More preferably, the aerosol - generating article has a ventilation level of from about 35% to about 50%. In some particularly preferred embodiments, the aerosol - generating article has a ventilation level of about 40%.

[0085] Without wishing to be bound by theory, the inventors have found that the temperature drop caused by the entry of cooler outside air through the ventilation zone into the hollow tubular section can have a beneficial effect on the nucleation and growth of aerosol particles.

[0086] The formation of aerosols from a gas mixture containing various chemicals depends on the delicate interplay between nucleation, evaporation and condensation, and coalescence, taking into account variations 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 sufficient probability (e.g., a probability of one - half) for a long time. These molecules represent a certain critical, threshold molecular cluster in transient molecular aggregates, which means that on average, smaller clusters may quickly break down into the gas phase, while larger clusters may grow on average. Such critical clusters are considered to be the key nucleation cores, and droplets are expected to grow from this core due to the condensation of molecules in the vapor. It is assumed that the freshly nucleated primordial droplets appear with a certain primordial diameter and then may grow by several orders of magnitude. This process is facilitated and enhanced by causing condensation through rapid cooling of the surrounding vapor. In this regard, it should be remembered that evaporation and condensation are two aspects of the same mechanism, namely gas - liquid mass transfer. While evaporation involves a net mass transfer from the droplet to the gas phase, condensation is a net mass transfer from the gas phase to the droplet phase. Evaporation (or condensation) will cause the droplet to shrink (or grow), but will not change the number of droplets.

[0087] In this context, which may be further complicated by coalescence phenomena, the temperature and rate of cooling play a crucial role in determining how the system responds. Generally speaking, different cooling rates can lead to significantly different temporal behaviors related to the formation of the liquid phase (droplets), since the nucleation process is usually non - linear. Without wishing to be bound by theory, it is assumed that cooling can lead to a rapid increase in the number concentration of droplets, followed by a strong, short - lived increase in this growth (nucleation burst). This nucleation burst seems to be more significant at lower temperatures. Additionally, it seems that higher cooling rates may favor an earlier onset of nucleation. In contrast, a decrease in the cooling rate seems to have a beneficial effect on the final size that the aerosol droplets ultimately reach.

[0088] Thus, the rapid cooling caused by the entry of external air into the hollow tubular section via the ventilation zone can be advantageously used to promote the nucleation and growth of aerosol droplets. However, at the same time, the entry of external air into the hollow tubular section has the direct disadvantage of diluting the aerosol stream delivered to the consumer.

[0089] The inventors have surprisingly found that when the ventilation level is between 30% and 50%, the dilution effect on the aerosol - especially as can be evaluated by measuring the delivery effect on glycerol contained in the aerosol - forming substrate which is an aerosol - forming agent - is advantageously minimized. In particular, a ventilation level between 35% and 42% has been found to yield particularly satisfactory glycerol delivery values.

[0090] In addition, the inventors have found that in the aerosol - generating article according to the present invention, the cooling and dilution effects caused by the entry of ventilation air at the location along the conduit defined by the above - mentioned hollow tubular section have a surprisingly reducing effect on the generation and delivery of phenolic substances.

[0091] The ventilation zone may include one or more rows of perforations formed through the peripheral wall of the hollow tubular section. Preferably, the ventilation zone includes only one row of perforations. This is understood to be advantageous because the cooling effect generated by ventilation can be condensed on a short portion of the cavity defined by the hollow tubular section, which can further enhance aerosol nucleation. This is because it is expected that a faster and more intense cooling of the volatile substance stream is particularly favorable for the formation of new aerosol particle nuclei.

[0092] Preferably, one or more rows of perforations are arranged circumferentially around the wall of the hollow tube. In the case where the ventilation zone includes two or more rows of perforations formed through the peripheral wall of the hollow tubular section, the rows are longitudinally spaced apart from each other along the hollow tubular section. For example, adjacent rows of perforations may be longitudinally spaced apart by a distance between about 0.25 mm and 0.75 mm.

[0093] The equivalent diameter of at least one of the ventilation perforations is preferably at least about 100 microns. Preferably, the equivalent diameter of at least one of the ventilation perforations is at least about 150 microns. Even more preferably, the equivalent diameter of at least one of the ventilation perforations is at least about 200 microns. Additionally, or as an alternative, the equivalent diameter of at least one of the ventilation perforations is preferably less than about 500 microns. More preferably, the equivalent diameter of at least one of the ventilation perforations is less than about 450 microns. Even more preferably, the equivalent diameter of at least one of the ventilation perforations is less than about 400 microns. The term "equivalent diameter" is used herein to denote the diameter of a circle having the same surface area as the cross - section of the ventilation perforation. The cross - section of the ventilation perforation can have any suitable shape. However, circular ventilation perforations are preferred.

[0094] The ventilation perforations can have a uniform size. As an alternative, the ventilation perforations can have different sizes. By varying the number and size of the ventilation perforations, the amount of external air entering the hollow tubular section can be adjusted when the consumer sucks on the mouthpiece of the aerosol-generating article during use. Thus, the ventilation level of the aerosol-generating article can advantageously be adjusted.

[0095] The ventilation perforations can be formed using any suitable technique, such as by laser technology, mechanical perforation of the hollow tubular section that is part of the aerosol-generating article, or pre-perforation before the hollow tubular section is combined with other elements to form the aerosol-generating article. Preferably, the ventilation perforations are formed by in-line laser perforation.

[0096] The length of the hollow tubular section is preferably at least about 10 millimeters. More preferably, the length of the hollow tubular section is at least about 15 millimeters. Additionally, or as an alternative, the length of the hollow tubular section is preferably less than about 30 millimeters. More preferably, the length of the hollow tubular section is less than about 25 millimeters. Even more preferably, the length of the hollow tubular section is less than about 20 millimeters. In some preferred embodiments, the length of the hollow tubular section is from about 10 millimeters to about 30 millimeters, more preferably from about 12 millimeters to about 25 millimeters, and even more preferably from about 15 millimeters to about 20 millimeters. By way of example, in a particularly preferred embodiment, the length of the hollow tubular section is about 18 millimeters. In another particularly preferred embodiment, the length of the hollow tubular section is about 13 millimeters.

[0097] The total length of the aerosol-generating article according to the present invention is preferably at least about 40 millimeters. Additionally, or as an alternative, the total length of the aerosol-generating article according to the present invention is preferably less than about 70 millimeters, more preferably less than 60 millimeters, and even more preferably less than 50 millimeters. In a preferred embodiment, the total length of the aerosol-generating article is between about 40 millimeters and about 70 millimeters. In an exemplary embodiment, the total length of the aerosol-generating article is about 45 millimeters.

[0098] The hollow tubular section is preferably formed from a substantially air-impermeable material. Thus, the air and aerosol particles drawn through the hollow tubular section are forced to flow from the upstream end of the hollow tubular section to its downstream end, but cannot flow through the peripheral wall of the hollow tubular element.

[0099] In some embodiments, the hollow tubular section comprises a wrapper material that also wraps the rod and the mouthpiece section. In fact, a wrapper material having a thickness falling within the above ranges is used to wrap and connect the rod and the mouthpiece section of the aerosol-generating substrate, and the wrapper material effectively forms the peripheral wall of the hollow tubular element.

[0100] For example, the basis weight of such a combined wrapper for the connecting rod and the mouthpiece section can be less than at least about 70 grams per square meter (gsm). Preferably, the basis weight of such a combined wrapper for the connecting rod and the mouthpiece section is at least about 80 gsm, more preferably at least about 90 gsm. In a particularly preferred embodiment, the basis weight of the combined wrapper for the connecting rod and the mouthpiece section is at least about 110 gsm, more preferably at least about 130 gsm.

[0101] In other embodiments, the hollow tubular section comprises a tube formed from a polymeric material or a cellulose material, and the heated aerosol-generating article further comprises a wrapper that wraps the rod, the tube, and the mouthpiece section. For example, the cellulose material can include paper or cardboard or a mixture thereof.

[0102] For example, the hollow tubular section can include a tube formed from an extruded plastic tube. As an alternative, the hollow tubular section can include a tube formed from a plurality of overlapping paper layers, such as a plurality of parallel wound paper layers or a plurality of helically wound paper layers. Forming a tube from a plurality of overlapping paper layers can help to further improve collapse resistance or deformation resistance. Preferably, the tube includes two or more paper layers. Alternatively or additionally, the tube preferably includes fewer than eleven paper layers.

[0103] Such a tube can be made airtight by using substantially airtight paper. The term "substantially airtight paper" is used herein to denote paper having an air permeability of less than about 20 CORESTA units, more preferably less than about 10 CORESTA units, and most preferably less than about 5 CORESTA units, as measured according to ISO 2965:2009. As an alternative, adjacent paper layers in the tube can be held together with an adhesive that imparts sealing properties to the tube.

[0104] Suitable materials for forming the tube are known in the art and include, but are not limited to, cellulose acetate, stiff paper (i.e., paper having a basis weight of at least 90 gsm), polymeric films (such as cellulose films), and cardboard.

[0105] In some embodiments, the ratio of the weight of the hollow tubular section to the volume of the inner cavity defined by the hollow tubular section is preferably less than 1 milligram per cubic millimeter. More preferably, the ratio of the weight of the hollow tubular section to the volume of the inner cavity defined by the hollow tubular section is less than 0.5 milligram per cubic millimeter.

[0106] In a particularly preferred embodiment, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section is less than 0.25 mg / mm³. More preferably, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section is less than 0.2 mg / mm³. Even more preferably, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section is less than 0.1 mg / mm³.

[0107] In a hollow tubular section in which the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section falls within the above range, the volume of the cavity is advantageously maximized while ensuring that the hollow tubular section contributes to the overall structural strength of the aerosol-generating article and effectively keeps the rod and the mouthpiece of the aerosol-generating substrate spaced apart.

[0108] In an exemplary embodiment, the hollow tubular section has an internal equivalent diameter of 7 mm and is formed from a packaging material having a basis weight of 110 g / m² and a weight of 2.5 mg / mm. For one such hollow tubular section, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section is approximately 0.065 mg / mm³.

[0109] In another exemplary embodiment, a hollow tubular section having an internal equivalent diameter of 5.3 mm may be provided as a cellulose acetate tube with a weight of 9.5 mg / mm. For one such hollow tubular section, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section is approximately 0.43 mg / mm³.

[0110] In an aerosol-generating article according to the present invention, the overall RTD of the article depends substantially on the RTD of the rod and on the RTD of the mouthpiece, since the hollow tubular section is substantially empty and thus contributes little, if at all, to the overall RTD. In fact, the hollow tubular section may be adapted to produce an RTD of from about 0 mm H₂O (about 00 Pa) to about 20 mm H₂O (about 200 Pa). Preferably, the hollow tubular section is adapted to generate an RTD between about 0 mm H₂O (about 00 Pa) and about 10 mm H₂O (about 100 Pa).

[0111] The aerosol-generating article preferably has an overall RTD of less than about 90 mm H₂O (about 900 Pa). More preferably, the aerosol-generating article has an overall RTD of less than about 80 mm H₂O (about 800 Pa). Even more preferably, the aerosol-generating article has an overall RTD of less than about 70 mm H₂O (about 700 Pa).

[0112] Alternatively, or as an alternative, the aerosol-generating article preferably has a total RTD of at least about 30 mm H2O (about 300 Pa). More preferably, the aerosol-generating article has a total RTD of at least about 40 mm H2O (about 400 Pa). Even more preferably, the aerosol-generating article has a total RTD of at least about 50 mm H2O (about 500 Pa).

[0113] The RTD of the aerosol-generating article can be evaluated as the negative pressure that must be applied to the downstream end of the mouthpiece under the test conditions defined in ISO 3402 in order to maintain a stable volumetric air flow of 17.5 ml / s through the mouthpiece. The RTD values listed above are intended to be measured separately on the aerosol-generating article (i.e., before inserting the article into the aerosol-generating device) without blocking the perforations of the ventilation zone.

[0114] If desired or required, for example in order to achieve a sufficiently high RTD of the aerosol-generating article, the length and density (denier per filament count) of the filter material of the mouthpiece can be adjusted. Alternatively, or as an alternative, additional filter sections can be included in the aerosol-generating article. By way of example, such additional filter sections can be included between the rod of the aerosol-generating substrate and the hollow tubular section. Preferably, such additional filter sections comprise a filter material such as cellulose acetate. Preferably, the length of the additional filter section is between about 4 mm and about 8 mm, preferably between about 5 mm and about 7 mm.

[0115] In some embodiments, the aerosol-generating article according to the present invention can include an additional support element, which is arranged between the rod of the aerosol-generating substrate and the hollow tubular section and is longitudinally aligned with the rod. More specifically, the support element is preferably provided immediately downstream of the rod and immediately upstream of the hollow tubular element.

[0116] The support element is provided as a tubular element. The support element can be formed from any suitable material or combination of materials. By way of example, the support element can be formed from one or more materials selected from the group consisting of cellulose acetate, cardboard, crimped paper, such as crimped heat-resistant paper or crimped parchment paper, and polymeric materials such as low-density polyethylene (LDPE). In a preferred embodiment, the support element is provided as a hollow cellulose acetate tube.

[0117] Preferably, the outer diameter of the support element is approximately equal to the outer diameter of the aerosol-generating article. The support element can have an outer diameter between about 5 mm and about 12 mm, such as between about 5 mm and about 10 mm or between about 6 mm and about 8 mm. In a preferred embodiment, the support element has an outer diameter of about 7.2 mm.

[0118] The peripheral wall of the support element may have a thickness of at least 1 mm, preferably at least about 1.5 mm, more preferably at least about 2 mm.

[0119] The support element may have a length between about 5 mm and about 15 mm. In a preferred embodiment, the support element has a length of about 8 mm.

[0120] During insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article, the user may need to apply some force in order to overcome the resistance of the aerosol-forming substrate of the aerosol-generating article to the insertion of the heating element of the aerosol-generating device. This may damage one or both of the aerosol-generating article and the heating element of the aerosol-generating device. Additionally, the force application during insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article may displace the aerosol-forming substrate within the aerosol-generating article. This may result in the heating element of the aerosol-generating device not being fully inserted into the aerosol-forming substrate, which may lead to non-uniform and ineffective heating of the aerosol-forming substrate of the aerosol-generating article. The support element is advantageously configured to resist downstream movement of the aerosol-forming substrate during insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article.

[0121] Preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 50 mm. More preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 45 mm. Even more preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 40 mm.

[0122] Additionally, or alternatively, the distance between the ventilation zone and the upstream end of the aerosol-generating article is preferably at least about 12 mm. More preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is preferably at least about 15 mm. Even more preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is preferably at least about 20 mm. In a particularly preferred embodiment, the distance between the ventilation zone and the upstream end of the aerosol-generating article is preferably at least about 25 mm.

[0123] Preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-forming substrate is at least about 2 mm. More preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-forming substrate is at least about 5 mm. Even more preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-forming substrate is at least about 10 mm. In some particularly preferred embodiments, the distance between the ventilation zone and the downstream end of the rod of the aerosol-forming substrate may be at least about 15 mm.

[0124] Alternatively, or as an alternative, the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is preferably less than about 35 millimeters. More preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 30 millimeters. Even more preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 25 millimeters.

[0125] In fact, the ventilation zone divides the cavity defined inside the hollow tubular section into an upstream sub-cavity and a downstream sub-cavity. The upstream sub-cavity extends longitudinally from the upstream end of the hollow tubular section to the location of the ventilation zone, and the downstream sub-cavity extends longitudinally from the location of the ventilation zone to the downstream end of the hollow tubular section. Without wishing to be bound by theory, it should be understood that in the upstream sub-cavity, the volatile substances of the aerosol stream are slowly cooled along the hollow tubular section by transferring some heat to the peripheral wall of the hollow tubular section, and thus aerosol particles begin to nucleate. On the other hand, in the downstream sub-cavity, the aerosol stream and the ventilation air are rapidly mixed, thereby rapidly cooling the volatile substances of the aerosol stream, and thus facilitating the nucleation of new aerosol particles and the growth of existing aerosol particles as the aerosol advances towards the mouthpiece.

[0126] Preferably, the ratio of the length of the upstream cavity to the length of the downstream cavity is less than 1.5. More preferably, the ratio of the length of the upstream cavity to the length of the downstream cavity is less than 1. Even more preferably, the ratio of the length of the upstream cavity to the length of the downstream cavity is less than 0.67.

[0127] Alternatively, or as an alternative, the ratio of the length of the upstream cavity to the length of the downstream cavity is preferably at least about 0.15. More preferably, the ratio of the length of the upstream cavity to the length of the downstream cavity is preferably at least about 0.2. Even more preferably, the ratio of the length of the upstream cavity to the length of the downstream cavity is preferably at least about 0.35.

[0128] Similarly, the ventilation zone divides the aerosol-generating article into two sections, namely upstream and downstream of the location of the ventilation zone.

[0129] Preferably, the ratio of the length of the upstream section of the aerosol-generating article to the length of the downstream section of the aerosol-generating article is less than 2.5. More preferably, the ratio of the length of the upstream section of the aerosol-generating article to the length of the downstream section of the aerosol-generating article is less than 2. Even more preferably, the ratio of the length of the upstream section of the aerosol-generating article to the length of the downstream section of the aerosol-generating article is less than 1.5. In a particularly preferred embodiment, the ratio of the length of the upstream section of the aerosol-generating article to the length of the downstream section of the aerosol-generating article is less than 1.

[0130] Alternatively, or as an alternative, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is preferably at least about 0.25. More preferably, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is at least 0.33. Even more preferably, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is at least about 0.5.

[0131] In the aerosol-generating article according to the present invention, it is advantageously easy to adjust and control the total RTD of the article. This is because the total RTD of the article depends on the RTD of a limited number of components, and the provision of the ventilation zone also helps to reduce the total RTD of the article. Therefore, it is advantageously possible to reduce the RTD variability between aerosol-generating articles.

[0132] Accordingly, the present invention can also provide a pack comprising ten or more aerosol-generating articles as described above, wherein the difference between the RTD of the aerosol-generating article having the highest RTD among at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD among at least ten aerosol-generating articles is less than 10 mm H2O (about 100 Pascals). Preferably, in one such pack, the difference between the RTD of the aerosol-generating article having the highest RTD among at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD is less than 9 mm H2O (about 90 Pascals), more preferably less than 8 mm H2O (about 80 Pascals), and even more preferably less than 7 mm H2O (about 70 Pascals). BRIEF DESCRIPTION OF THE DRAWINGS

[0133] Hereinafter, the present invention will be further described with reference to the figures of the drawings, in which:

[0134] Figure 1 shows a schematic side cross-sectional view of an aerosol-generating article according to the present invention;

[0135] Figure 2 shows a schematic side cross-sectional view of another example of an aerosol-generating article according to the present invention; and

[0136] Figure 3 shows a schematic side cross-sectional view of a further example of an aerosol-generating article according to the present invention. DETAILED DESCRIPTION

[0137] Figure 1The aerosol-generating article 10 shown therein comprises a stem 12 of aerosol-generating substrate, a hollow cellulose acetate tube 14, a hollow tubular section 16 and a mouthpiece section 18. These four elements are arranged in an end-to-end, longitudinally aligned manner and are wrapped by a packaging material 20 to form the aerosol-generating article 10. The aerosol-generating article 10 has a mouth end 22 and an upstream distal end 24 located at the end of the article opposite to the mouth end 22. Figure 1 The aerosol-generating article 10 shown therein is particularly suitable for use with an electrically operated aerosol-generating device that includes a heater for heating the stem of the aerosol-generating substrate.

[0138] The stem 12 of the aerosol-generating substrate has a length of about 12 mm and a diameter of about 7 mm. The stem 12 is cylindrical and has a substantially circular cross-section. The stem 12 comprises a sheet of aggregated homogeneous tobacco material. The sheet of homogeneous tobacco material comprises 10% glycerol by dry weight. The hollow cellulose acetate tube 14 has a length of about 8 mm and a thickness of about 1 mm.

[0139] The mouthpiece section 18 comprises a cellulose acetate tow plug of 8 denier per filament and has a length of about 7 mm.

[0140] The hollow tubular section 16 is provided as a cylindrical tube having a length of about 18 mm and the thickness of the tube wall is about 100 microns.

[0141] More specifically, the hollow tubular section 16 can be formed, for example, from paper having a dry weight of 110 gsm and a weight of 45 mg (i.e., 2.5 mg / mm length). The equivalent inner diameter of the hollow tubular section 16 is about 7 mm. Thus, the volume of the cavity defined inside the hollow tubular section 16 is about 693 cubic millimeters. Thus, the ratio between the weight of the hollow tubular section 16 and the volume of the inner cavity defined by the hollow tubular section 16 is about 0.065. The aerosol-generating article 10 includes a ventilation zone 26 which is provided about 5 mm from the upstream end of the mouthpiece section 18. Thus, the ventilation zone 26 is located about 12 mm from the downstream end of the aerosol-generating article, about 13 mm from the upstream end of the hollow tubular section.

[0142] Thus, the ventilation zone 26 is located about 21 mm from the downstream end of the stem 12. Figure 2 Show another example of an aerosol-generating article according to the present invention. Figure 2 The aerosol-generating article 30 has the same structure as Figure 1 the aerosol-generating article 10 and is substantially different from the aerosol-generating article 10 only in the length of certain components, and will be described below only within the scope in which it is different from the aerosol-generating article 10. Hereinafter, for corresponding components having the same structure or functional function, the same reference numerals will be used as much as possible.

[0143] In Figure 2 the aerosol-generating article 30, the rod 12 and the hollow cellulose acetate tube 14 have the same length as in Figure 1 the aerosol-generating article 10. However, the mouthpiece section includes a cellulose acetate plug of 11 denier per filament and having a length of about 12 mm, and a hollow tubular section 14 having a length of about 13 mm. The ventilation zone 26 is provided about 6 mm from the upstream end of the mouthpiece section 18 and about 7 mm from the upstream end of the hollow tubular section. Thus, the ventilation zone 26 is located about 15 mm from the downstream end of the rod 12.

[0144] In Figure 2 an embodiment, the hollow tubular section 16 can be provided, for example, as a cylindrical tube of cellulose acetate having a length of about 18 mm and a peripheral wall thickness of about 1 mm, weighing 171 mg (i.e., 9.5 mg / mm of length).

[0145] The equivalent inner diameter of the hollow tubular section 16 can be about 5.3 mm. Thus, the volume of the cavity defined inside the hollow tubular section 16 is about 397 cubic millimeters. Thus, the ratio between the weight of the hollow tubular section and the volume of the inner cavity defined by the hollow tubular section 16 is about 0.43. Figure 3 Shows yet another example of an aerosol-generating article according to the present invention. Figure 3 The aerosol-generating article 40 of Figure 1 differs structurally from the aerosol-generating article 10 of Figure 2 and the aerosol-generating article 30 of

[0146] in that it does not include a hollow cellulose acetate tube as a support element. Thus, the lengths of the three main components are also different. Hereinafter, for corresponding components having the same structure or functional function, the same reference numerals will be used as much as possible. Figure 3 In

[0147] the aerosol-generating article 40, the rod 12 has a length of about 12 mm, the hollow tubular section 14 has a length of about 26 mm, and the mouthpiece section 18 includes a cellulose acetate tow plug having a length of about 12 mm and 11 denier per filament. The ventilation zone 26 is provided about 5 mm from the upstream end of the mouthpiece section 18 and about 21 mm from the upstream end of the hollow tubular section, where in this embodiment, the upstream end of the hollow tubular section coincides with the downstream end of the rod 12.

[0148] Example 1 This experiment was conducted to evaluate the effect of incorporating a hollow tubular section, where the ventilation zone is provided along the position of the hollow tubular section according to the present invention. The experiment studied the influence of the ventilation level on the delivery of nicotine and the aerosol former (glycerol). The present invention also provides a comparative measurement of a reference aerosol generating article without ventilation.

[0149] Materials and Methods

[0150] Article A is an aerosol generating article formed from: a rod of aerosol generating substrate, the rod comprising a sheet of aggregated homogeneous tobacco material and approximately 18% glycerol by dry weight, the rod having a length of 12 mm; a support element in the form of a hollow cellulose acetate tube aligned with and downstream of the rod, the support element having a length of 8 mm; a hollow tubular section in the form of a cardboard tube aligned with and downstream of the rod, the hollow tubular section having a length of 13 mm; a mouthpiece section of filter material aligned with and downstream of the hollow tubular section, the mouthpiece section having a length of 12 mm. The ventilation zone is provided along the hollow tubular section at a position 18 mm from the downstream end of the mouthpiece section. The ventilation level of the aerosol generating article A is 30%.

[0151] Article B is a reference aerosol generating article having the same structure as Article A but without a ventilation zone. Thus, the ventilation level of the aerosol generating article B is 0%.

[0152] The delivery of nicotine and glycerol was measured by gas chromatography / time-of-flight mass spectrometry (GC / MS-TOF) for nicotine and glycerol collected on Cambridge filter pads. Runs were conducted as described in Example 1

[0153] Results Table 1 below shows the average nicotine and glycerol delivery of Article A and Article B.

[0154] Table 1. Influence of ventilation level on nicotine and glycerol delivery.

[0155]

[0156]

Claims

1. An aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising: a stem of aerosol-forming substrate, wherein the stem of aerosol-forming substrate comprises at least one aerosol-forming agent and has an aerosol-forming agent content of at least 10% by dry weight; a mouthpiece section comprising a plug of filter material, the mouthpiece section being disposed downstream of the stem and longitudinally aligned with a first section; a hollow tubular section located at a position between the stem and the mouthpiece section, wherein the hollow tubular section is longitudinally aligned with the stem and the mouthpiece section, and the hollow tubular section defines a cavity extending upstream to the upstream end of the mouthpiece section; and a ventilation zone located along the hollow tubular section, wherein the equivalent inner diameter of the hollow tubular section at the position of the ventilation zone is at least 5 mm.

2. The aerosol-generating article according to claim 1, wherein the hollow tubular section comprises a wrapper material that also wraps the stem and the mouthpiece section.

3. The aerosol-generating article according to claim 1, wherein the hollow tubular section comprises a tube formed of a cellulose material.

4. The aerosol-generating article according to claim 3, the aerosol-generating article further comprising a wrapper material that wraps the stem, the tube, and the mouthpiece section.

5. The aerosol-generating article according to any one of claims 1 to 4, wherein the equivalent inner diameter of the hollow tubular section is substantially constant along the length of the hollow tubular section.

6. The aerosol-generating article according to any one of claims 1 to 4, wherein the ventilation zone comprises one or more rows of perforations formed through the circumferential wall of the hollow tubular section.

7. The aerosol-generating article according to any one of claims 1 to 4, wherein the ventilation zone is located along the hollow tubular section at least 2 mm from the upstream end of the mouthpiece section.

8. The aerosol-generating article according to any one of claims 1 to 4, wherein the ventilation zone is located along the hollow tubular section less than 18 mm from the upstream end of the hollow tubular section.

9. The aerosol-generating article according to any one of claims 1 to 4, wherein the aerosol-generating article has a ventilation level of at least 10%.

10. The aerosol-generating article according to any one of claims 1 to 4, wherein the aerosol-generating article has a ventilation level of less than 60%.

11. The aerosol-generating article according to any one of claims 1 to 4, wherein the length of the hollow tubular section is between 10 mm and 30 mm.

12. The aerosol-generating article according to any one of claims 1 to 4, wherein the stem of the aerosol-forming substrate has a length of less than 40 mm.

13. The aerosol-generating article according to claim 12, wherein the stem of the aerosol-forming substrate has a length of less than 15 mm.

14. The aerosol-generating article according to any one of claims 1 to 4, wherein the total length of the aerosol-generating article is between 40 mm and 70 mm.

15. The aerosol-generating article according to any one of claims 1 to 4, wherein the thickness of the peripheral wall of the hollow tubular section at the position of the ventilation zone is less than 1.5 millimeters.

16. The aerosol-generating article according to any one of claims 1 to 4, wherein the thickness of the peripheral wall of the hollow tubular section is at least 100 micrometers.

17. The aerosol-generating article according to any one of claims 1 to 4, wherein the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the position of the ventilation zone is less than 3.

5.

18. The aerosol-generating article according to claim 17, wherein the ratio between the distance between the ventilation zone and the upstream end of the hollow tubular section and the equivalent inner diameter of the hollow tubular section at the position of the ventilation zone is less than 2.5.

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