JP7743567B2 - Aerosol-generating article containing a light hollow segment - Google Patents

Description

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

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

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 the aerosol-generating substrate of the heated aerosol-generating article.

Substrates for heated aerosol-generating articles have typically been produced using randomly oriented pieces, strands, or strips of tobacco material. Alternatively, rods for heated aerosol-generating articles formed from an assembly of sheets of tobacco material have been proposed, for example, in International Patent Application WO-A-2012/164009. The rods disclosed in WO-A-2012/164009 have longitudinal porosity that allows air to be drawn through the rod. In effect, the folds in the assembly of sheets of tobacco material define longitudinal channels through the rod.

Alternative rods for heated aerosol-generating articles are known from International Patent Application WO-A-2011/101164. These rods are formed from strands of homogenized tobacco material and may be formed by casting, rolling, calendering, or extruding a mixture comprising particulate tobacco and at least one aerosol former to form a sheet of homogenized tobacco material. In alternative embodiments, the rods of WO-A-2011/101164 may also be formed from strands of homogenized tobacco material obtained by extruding a mixture comprising particulate tobacco and at least one aerosol former to form a continuous length of homogenized tobacco material.

Substrates for heated aerosol-generating articles typically further comprise an aerosol former, i.e., a compound or mixture of compounds that promotes the formation of an aerosol during use and that is preferably substantially resistant to thermal decomposition at the use temperature of the aerosol-generating article. Examples of suitable aerosol formers include polyhydric alcohols (such as propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol mono-, di-, or triacetate), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate).

It is also common for an aerosol-generating article to include one or more additional elements assembled with the substrate within the same wrapper to generate an inhalable aerosol upon heating. Examples of such additional elements include a mouthpiece filtering segment, a support element adapted to provide structural strength to the aerosol-generating article, a cooling element adapted to favor cooling of the aerosol before it reaches the mouthpiece, etc. However, while the inclusion of such additional elements has been proposed in light of their beneficial effects, they generally complicate the overall structure of the aerosol-generating article, making it more complex and expensive to manufacture. In practice, the manufacture of such multi-element aerosol-generating articles generally requires more complex manufacturing machines and machine combinations.

In this regard, aerosol-generating articles with simpler structures have been proposed. However, in the absence of certain additional components, such as an aerosol cooling element, it can be more difficult to manufacture an aerosol-generating article that consistently provides aerosol delivery and RTD that are satisfactory to consumers.

It is therefore desirable to provide an aerosol-generating article that is capable of consistently providing satisfactory aerosol delivery to the consumer during use. Furthermore, it is desirable to provide improved aerosol-generating articles that have such satisfactory RTD values. It is equally desirable to provide such aerosol-generating articles that are manufactured efficiently and quickly, and that preferably have low RTD variation between articles. The present invention aims to provide a technical solution adapted to achieve at least one of the above-mentioned desirable results.

According to one aspect of the present invention, there is provided an aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising a rod of aerosol-generating substrate and a hollow tubular segment located downstream of the rod. The hollow tubular segment is longitudinally aligned with the rod and defines a cavity extending entirely from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment. Furthermore, the hollow tubular segment has a length of less than about 25 millimeters. The aerosol-generating article further comprises a vent zone located along the hollow tubular segment. The ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram per cubic millimeter. The rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol former content of at least about 10 percent on a dry weight basis.

As used herein, the term "aerosol-generating article" refers to 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" refers to a substrate that, upon heating, has the ability to release volatile compounds to generate an aerosol.

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 (e.g., tobacco). Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is produced by the transfer of heat from a combustible fuel element or heat source to a physically separated aerosol-forming material. For example, an aerosol-generating article according to the present invention finds particular application in aerosol-generating systems that include an electrically heated aerosol generator having an internal heater blade adapted to be inserted into a rod of an aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art, for example, in European Patent No. EP 0822670.

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

As used herein, the term "tubular segment" refers to an elongated element that defines a lumen or airflow passage along its longitudinal axis. In particular, the term "tubular" is used hereinafter to refer to a tubular element that has a substantially cylindrical cross-section and defines at least one airflow conduit that establishes uninterrupted fluid communication between the upstream end of the tubular element and the downstream end of the tubular element. However, it will be understood that alternative geometries of the cross-section of the tubular element may be possible.

As used herein, the term "longitudinal" refers to a direction corresponding to the major longitudinal axis of the aerosol-generating article extending between the upstream and downstream ends of the aerosol-generating article. As used herein, the terms "upstream" and "downstream" describe the relative position 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.

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

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

The term "peripheral wall thickness of a tubular element" is used herein to mean the smallest distance measured between the outer and inner surfaces of the wall that bounds the periphery of the tubular element. 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 tubular elements with a substantially circular cross-section, the distance is measured along a substantially radial direction of the tubular element.

In some embodiments, the peripheral wall thickness of the tubular element is constant. In alternative embodiments, the peripheral wall thickness of the tubular element varies along the length of the tubular element. This may be because the tubular element is formed from a material with 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 a tapered section, etc. In embodiments in which the peripheral wall thickness of the tubular element varies along the length of the tubular element, the "peripheral wall thickness of the tubular element" is considered to be an average value calculated based on several values measured as the smallest distance between the outer and inner surfaces of the wall at different positions along the length of the tubular element.

In either embodiment, a particularly significant parameter is the thickness of the peripheral wall of the tubular element at the location of the ventilation zone.

The expression "air-impermeable material" is used throughout this specification to mean a material that does not allow the passage of fluids, particularly air and smoke, through gaps or pores in the material. When a hollow tubular segment is formed of a material that is impermeable to air and aerosol particles, air and aerosol particles drawn through the hollow tubular segment are forced to flow through the airflow conduit defined internally by the hollow tubular segment, but cannot flow across the peripheral wall of the hollow tubular segment.

As used herein, the term "homogenized tobacco material" includes any tobacco material formed by agglomeration of particles of tobacco material. A sheet or web of homogenized tobacco material is formed by agglomerating particulate tobacco obtained by grinding or otherwise pulverizing one or both of tobacco lamina and tobacco stems. Additionally, homogenized tobacco material may contain small amounts of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during tobacco processing, handling, and shipping. Sheets of homogenized tobacco material may be produced by casting, extrusion, papermaking processes, or any other suitable process known in the art.

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

The term "ventilation level" is used throughout this specification to mean the volume ratio of the airflow entering the aerosol-generating article through the ventilation zone (ventilation airflow) to the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the greater the dilution of the aerosol stream delivered to the consumer.

As briefly described above, the aerosol-generating article of the present invention comprises a rod of aerosol-generating substrate and a hollow tubular segment located downstream of the rod. These two elements are longitudinally aligned. The rod of aerosol-generating substrate comprises at least one aerosol former.

In contrast to known aerosol-generating articles, the rod of aerosol-generating substrate has an aerosol-former content of at least about 10 percent on a dry weight basis. Furthermore, the hollow tubular segment defines a cavity extending entirely from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment, and has a length of less than about 25 millimeters. A vent zone is provided at a location along the hollow tubular segment. Furthermore, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram per cubic millimeter.

By providing an aerosol-generating article in which a hollow tubular element defining a recess extending entirely from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment is disposed between the rod of the aerosol-generating substrate and the mouth end of the aerosol-generating article, 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 manufacturing and assembling the equipment required to carry out the manufacturing process.

One such aerosol-generating article does not include an aerosol cooling element adapted to reduce the temperature of the aerosol stream drawn through the aerosol-generating article, as is the case, for example, with the aerosol-generating article described in International Patent Application WO 2013/120565.

The inventors have discovered that satisfactory cooling of the aerosol stream generated upon heating of the article and drawn through the hollow tubular element can be achieved by providing a ventilation zone at a location along the hollow tubular segment. Furthermore, the inventors have unexpectedly discovered that it may be possible to offset the effects of increased aerosol dilution caused by admitting ventilation air into the article by utilizing a hollow tubular segment having a length of less than about 25 millimeters, in which the ratio of the weight of the hollow tubular segment to the volume of the interior cavity defined by the hollow tubular segment is less than 1 milligram per cubic millimeter.

Without being bound by theory, it is believed that the introduction of vent air rapidly reduces the temperature of the aerosol stream as the aerosol moves toward the mouth end, so that the vent air enters the aerosol stream relatively close to the upstream end of the hollow tubular segment (i.e., sufficiently close to the heat source and the rod of the aerosol-generating substrate), achieving dramatic cooling of the aerosol stream, which has a favorable effect on aerosol particle condensation and nucleation. Therefore, the overall ratio of aerosol particle phase to aerosol gas phase can be improved compared to existing non-vented aerosol-generating articles.

Providing such a large volume cavity, as in the case of an article according to the present invention, effectively provides a cooling chamber within which nucleation can be enhanced by slowing the aerosol flow, thereby favoring condensation of aerosol particles upstream of the mouth end of the article. Without being bound by theory, it is understood that providing a sufficiently wide tubular cavity downstream of the rod of the aerosol-generating substrate favors the formation of a sufficient amount of aerosol during use. As a result, a greater proportion of the generated aerosol particles begin to condense before reaching the mouth end of the article.

At the same time, hollow tubular segments within the aforementioned ranges provide sufficient structural strength to the article and maintain the rod of the aerosol-generating article at a predetermined distance from the mouth end of the article. Such hollow tubular segments therefore provide a sufficiently long chamber for the aerosol stream to flow through, and therefore, during use, allow sufficient time for the temperature of volatilized species to be reduced and for aerosol particle nucleation to occur. Furthermore, it has been found that relatively short hollow tubular segments within the aerosol-generating article of the present invention allow good aerosol nucleation, while at the same time not presenting too large a surface area for the aerosol particles to condense upon.

In practice, in an aerosol-generating article according to the present invention, the cross-sectional surface area of the recesses in the hollow tubular segment may be maximized while at the same time ensuring that the hollow tubular segment has the structural strength necessary to prevent collapse of the aerosol-generating article and to provide a degree of support for the rod of the aerosol-generating substrate, and that the RTD of the hollow tubular segment is minimized. It is understood that a large value for the cross-sectional surface area of the recesses in the hollow tubular segment is associated with a reduced velocity of the aerosol flow traveling along the aerosol-generating article, which is further expected to favor nucleation.

Furthermore, it is understood that by utilizing hollow tubular segments having a small thickness, such as less than 1.5 millimeters, it is possible to substantially prevent diffusion of the aeration air before it contacts and mixes with the aerosol stream, further favoring the nucleation phenomenon. In effect, it is possible to improve the cooling effect on the formation of new aerosol particles by providing more controllably localized cooling of the volatilized species stream.

In fact, the inventors have surprisingly discovered how the beneficial effects of enhanced nucleation significantly offset the undesirable effects of dilution, such that satisfactory aerosol delivery values are consistently achieved with aerosol-generating articles according to the present invention. This is particularly advantageous for "short" aerosol-generating articles, such as those in which the length of the aerosol-generating substrate rod is less than about 40 millimeters, preferably less than 25 millimeters, and even more preferably less than 20 millimeters, or the overall length of the aerosol-generating article is less than about 70 millimeters, preferably less than about 60 millimeters, and even more preferably less than 50 millimeters. As can be seen, with such aerosol-generating articles, there is less time and space for aerosol formation and for the particle phase of the aerosol to become available for delivery to the consumer.

Furthermore, because the hollow tubular elements do not substantially contribute to the RTD of the aerosol-generating article, the overall RTD of the article can advantageously be fine-tuned in an aerosol-generating article according to the present invention by adjusting the length and density of the rods in the aerosol-generating substrate, or, in embodiments where a mouthpiece segment is present, the length and density of the segments of filtering material in the mouthpiece segment. This allows aerosol-generating substrates to be consistently and very accurately manufactured with a predetermined RTD to provide a satisfactory level of RTD to the consumer, even in the presence of ventilation.

The aerosol-generating articles of the present invention can be manufactured in a continuous process that can be carried out quickly and efficiently, and can be easily produced on existing production lines for the manufacture of heated aerosol-generating articles without requiring extensive modifications to the manufacturing equipment.

The rod of the aerosol-generating substrate preferably has an outer diameter approximately equal to the outer diameter of the aerosol-generating article.

The aerosol-generating substrate rod preferably has an outer diameter of at least 5 millimeters. The aerosol-generating substrate rod may have an outer diameter of about 5 millimeters to about 12 millimeters, for example, about 5 millimeters to about 10 millimeters, or about 6 millimeters to about 8 millimeters. In a preferred embodiment, the aerosol-generating substrate rod has an outer diameter of 7.2 millimeters within ±10 percent.

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

The aerosol-generating substrate rod preferably has a substantially uniform cross-section along the length of the rod. It is particularly preferred that the aerosol-generating substrate rod have a substantially circular cross-section.

In a preferred embodiment, the aerosol-forming substrate comprises an assembly of one or more crimped sheets of homogenized tobacco material. Preferably, the one or more sheets of homogenized tobacco material are textured. As used herein, the term "textured sheet" means a sheet that has been crimped, embossed, debossed, perforated, or otherwise modified. Textured sheets of homogenized tobacco material for use in the present invention may comprise a plurality of spaced indentations, protrusions, perforations, or combinations thereof. According to a particularly preferred embodiment of the present invention, the rod of aerosol-generating substrate comprises an assembly of crimped sheets of homogenized tobacco material surrounded by a wrapper.

As used herein, the term "crimped sheet" is intended to be synonymous with the term "crimped sheet" and refers to 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 of the present invention. This conveniently facilitates assembly of the crimped sheet of homogenized tobacco material to form a rod. However, it will be appreciated that crimped sheets of homogenized tobacco material for use in the present invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that form an acute or obtuse angle with respect to the cylindrical axis of the rod. In certain embodiments, a homogenized tobacco material sheet for use in a rod of an article of the present invention may be textured substantially evenly across substantially its entire surface. For example, a crimped sheet of homogenized tobacco material for use in the manufacture of a rod for use in an aerosol-generating article of the present invention may include a plurality of substantially parallel ridges or corrugations that are substantially uniformly spaced across the width of the sheet.

A sheet or web of homogenized tobacco material for use in the present invention may have a tobacco content of at least about 40 weight percent on a dry weight basis, more preferably at least about 60 weight percent on a dry weight basis, even 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.

A sheet or web of homogenized tobacco material for use in an aerosol-generating substrate may include one or more intrinsic binders (i.e., tobacco-intrinsic binders), one or more extrinsic binders (i.e., tobacco-extrinsic binders), or a combination thereof, to assist in agglomerating the particulate tobacco. Alternatively, or additionally, a sheet of homogenized tobacco material for use in an aerosol-generating substrate may include other additives, including, but not limited to, tobacco and non-tobacco fibers, aerosol-forming agents, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents, and combinations thereof.

Suitable extrinsic binders for inclusion in sheets or webs of homogenized tobacco material for use in aerosol-generating substrates are well known in the art and include, but are not limited to, gums (e.g., guar gum, xanthan gum, gum arabic, and locust bean gum), cellulosic binders (e.g., hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, and ethyl cellulose), polysaccharides (e.g., starch), organic acids (e.g., alginic acid), conjugate base salts of organic acids (e.g., sodium alginate, agar, and pectin), and combinations thereof.

Suitable non-tobacco fibers for inclusion in sheets or webs of homogenized tobacco material for use in aerosol-generating substrates are well known in the art and include, but are not limited to, cellulose fibers, soft wood fibers, hard wood fibers, jute fibers, and combinations thereof. Prior to inclusion in sheets of homogenized tobacco material for use in aerosol-generating substrates, the non-tobacco fibers may be processed by any suitable process known in the art, including, but not limited to, mechanical pulping; refining; chemical pulping; bleaching; sulfate pulping; and combinations thereof.

Preferably, the sheet or web of homogenized tobacco material includes an aerosol former. As used herein, the term "aerosol former" describes any suitable known compound or mixture of compounds that facilitates the formation of an aerosol during use and that is substantially resistant to thermal decomposition at the operating temperatures of the aerosol-generating article.

Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, and triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate).

Preferred aerosol formers are polyhydric alcohols (e.g., propylene glycol, triethylene glycol, 1,3-butanediol, and most preferably glycerin) or mixtures thereof.

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

The homogenized sheet or web of tobacco material has an aerosol former content of greater than 10 percent on a dry weight basis. Preferably, the homogenized sheet or web of tobacco material has an aerosol former content of greater than 12 percent on a dry weight basis. More preferably, the homogenized sheet or web of tobacco material has an aerosol former content of greater than 14 percent on a dry weight basis. Even more preferably, the homogenized sheet or web of tobacco material has an aerosol former content of greater than 16 percent on a dry weight basis.

The sheet of homogenized tobacco material may have an aerosol former content of approximately 10 percent to approximately 30 percent on a dry weight basis. Preferably, the sheet or web of homogenized tobacco material has an aerosol former content of less than 25 percent on a dry weight basis.

In one preferred embodiment, the homogenized tobacco material sheet has an aerosol former content of approximately 20 percent on a dry weight basis.

The homogenized tobacco sheet or web for use in the aerosol-generating articles of the present invention may be made by methods known in the art (e.g., the method disclosed in International Patent Application No. WO-A-2012/164009 A2). In one preferred embodiment, the sheet of homogenized tobacco material for use in the aerosol-generating article is formed by a casting process from a slurry containing particulate tobacco, guar gum, cellulose fibers, and glycerin.

Alternative arrangements of homogenized tobacco material within a rod for use in an aerosol-generating article are known to those skilled in the art and may include multiple stacked sheets of homogenized tobacco material, multiple elongated tubular elements formed by winding strips of homogenized tobacco material around a longitudinal axis, etc.

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

In the aerosol-generating substrate rod of the article according to the present invention, the aerosol-generating substrate is preferably surrounded by a wrapper. The wrapper may be formed of a porous or non-porous sheet material. The wrapper may be formed of any suitable material or combination of materials. Preferably, the wrapper is a paper wrapper.

Aerosol-generating articles according to the present invention may optionally include a mouthpiece segment located downstream of the hollow tubular segment, preferably adjacent end-to-end to the hollow tubular segment. In these articles, the recess in the hollow tubular segment extends all the way to the upstream end of the mouthpiece segment.

The mouthpiece typically includes a plug of filtration material capable of removing particulate components, gaseous components, or a combination. Suitable filtration materials are well known in the art and include, but are not limited to, fibrous filtration materials such as cellulose acetate tow, viscose fibers, polyhydroxyalkanoic acid (PHA) fibers, polylactic acid (PLA) fibers, and paper; adsorbents such as activated alumina, zeolites, molecular sieves, and silica gel; and combinations thereof. Additionally, the plug of filtration material may further include one or more aerosol modifiers. Suitable aerosol modifiers are well known in the art and include, but are not limited to, flavorings such as menthol. In some embodiments, the mouthpiece may further include a mouth-end recess downstream from the plug of filtration material. By way of example, the mouthpiece may include a hollow tube longitudinally aligned with and positioned immediately downstream from the plug of filtration material, the hollow tube forming a mouth-end recess that is open to the outside environment at the downstream end of the mouthpiece.

The mouthpiece preferably has a length of at least about 4 millimeters, more preferably at least about 6 millimeters, and even more preferably at least about 8 millimeters. Additionally or alternatively, the mouthpiece preferably has a length of less than 25 millimeters, more preferably less than 20 millimeters, and even more preferably less than 15 millimeters. In some preferred embodiments, the mouthpiece has a length of between about 4 millimeters and about 25 millimeters, and more preferably between about 6 millimeters and about 20 millimeters. In an exemplary embodiment, the mouthpiece has a length of about 7 millimeters. In another exemplary embodiment, the mouthpiece has a length of about 12 millimeters.

In other embodiments, a segment of filtering material or similar may alternatively or additionally be provided between the rod and the hollow tubular segment of the aerosol-generating substrate.

The hollow tubular segment is preferably an annular tube that defines an air gap within the aerosol-generating article. In effect, the hollow tubular segment provides a chamber into which volatilized aerosol components released upon heating of the aerosol-generating substrate accumulate and flow. As briefly described above, this chamber extends longitudinally from the upstream end of the hollow tubular segment all the way to the downstream end of the hollow tubular segment.

Thus, in an aerosol-generating article according to the present invention, the hollow tubular segment maintains the rod of aerosol-generating substrate a predetermined distance from the mouth end of the article and provides an elongated airflow conduit through which an aerosol forms and flows toward the mouth end of the article. During use, a thermal gradient is established along this airflow conduit. In effect, a temperature difference is provided such that the temperature of the volatilized aerosol components entering the hollow tubular segment at its upstream end is greater than the temperature of the volatilized aerosol components exiting the hollow tubular segment at its downstream end (i.e., the end upstream of the mouthpiece, if present).

On the other hand, the hollow tubular segment must be able to withstand any axial compressive load or bending moment that may be applied to the hollow tubular segment during manufacture of the aerosol-generating article. Furthermore, the hollow tubular segment must provide structural strength to the aerosol-generating article so 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 internally by the hollow tubular element be as large as possible, to favor aerosol formation and improve delivery of the aerosol to the consumer.

To meet these requirements, as briefly described above, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram per cubic millimeter. More preferably, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.5 milligrams per cubic millimeter. Even more preferably, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.2 milligrams per cubic millimeter. In a particularly preferred embodiment, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.1 milligrams per cubic millimeter.

In hollow tubular segments having a ratio of hollow tubular segment weight to volume of the internal cavity defined by the hollow tubular segment within the above-mentioned ranges, the cavity volume is advantageously maximized, while the hollow tubular segment contributes to the overall structural strength of the aerosol-generating article and ensures that the rod of the aerosol-generating substrate is effectively maintained spaced from the mouth end of the article.

In an exemplary embodiment, the hollow tubular segment has an equivalent diameter of 7 millimeters, is formed from a wrapper having a basis weight of 110 gsm, and weighs 2.5 milligrams per millimeter. For one such hollow tubular segment, the ratio of the weight of the hollow tubular segment to the volume of the interior cavity defined by the hollow tubular segment is approximately 0.065 milligrams per cubic millimeter.

In another exemplary embodiment, a hollow tubular segment having an equivalent inner diameter of 5.3 millimeters may be provided as a cellulose acetate tube having a weight of 9.5 milligrams per cubic millimeter. For one such hollow tubular segment, the ratio of the weight of the hollow tubular segment to the volume of the interior cavity defined by the hollow tubular segment is approximately 0.43 milligrams per cubic millimeter.

Preferably, the peripheral wall thickness of the hollow tubular segment is less than 1.5 millimeters. Preferably, the peripheral wall thickness of the hollow tubular segment is less than 1250 micrometers, more preferably less than 1000 micrometers, and even more preferably less than 900 micrometers. In a particularly preferred embodiment, the peripheral wall thickness of the hollow tubular segment is less than 800 micrometers.

Additionally or alternatively, the peripheral wall thickness of the hollow tubular segment is at least about 100 micrometers. Preferably, the peripheral wall thickness of the hollow tubular segment is at least about 200 micrometers.

Without being bound by theory, it is believed that utilizing a hollow tubular segment having a peripheral wall thickness within the aforementioned range advantageously limits or even substantially prevents diffusion of the flowing air prior to its contact and mixing with the aerosol stream. This is further understood to favor the nucleation phenomenon. In effect, by providing more controllably localized cooling of the stream of volatilized species drawn through the hollow tubular segment, the effect of cooling on the formation of new aerosol particles can be improved.

The equivalent inner diameter of the hollow tubular segment is preferably at least about 4 millimeters. The term "equivalent inner diameter," as used herein, means the diameter of a circle having the same surface area as the cross-section of the airflow conduit internally defined by the hollow tubular segment. The cross-section of the airflow conduit may have any suitable shape. However, as briefly mentioned above, a circular cross-section is preferred, i.e., the hollow tubular segment is a substantially cylindrical tube. In that case, the equivalent inner diameter of the hollow tubular segment will correspond to the inner diameter of the substantially cylindrical tube.

More preferably, the equivalent inner diameter of the hollow tubular segment is at least about 5 millimeters, even more preferably at least about 5.25 millimeters, and most preferably at least about 5.5 millimeters. In some embodiments, the equivalent inner diameter of the hollow tubular segment is at least about 6 millimeters, or at least about 6.5 millimeters, or at least about 7 millimeters.

Furthermore, it is preferred that the equivalent inner diameter of the hollow tubular segment be less than about 10 millimeters. More preferably, the equivalent inner diameter of the hollow tubular segment be less than about 9.5 millimeters, and even more preferably, be less than 9 millimeters.

The equivalent inner diameter of the hollow tubular segment is measured at the location of the ventilation zone.

In preferred embodiments, the equivalent inner diameter of the hollow tubular segment is substantially constant along the length of the hollow tubular segment. In other embodiments, the equivalent inner diameter of the hollow tubular segment may vary along the length of the hollow tubular segment.

Surprisingly, the inventors have found that aerosol-generating articles according to the present invention, including hollow tubular segments having equivalent inner diameters within the aforementioned ranges, can provide particularly satisfactory aerosol delivery values. Without being bound by theory, it is believed that an aerosol stream flowing along a hollow tubular segment having an equivalent inner diameter within the aforementioned ranges flows at a relatively slow velocity as the incoming cooler flowing air stream is received by and mixes with the aerosol stream. Because the aerosol stream moves relatively slowly along the hollow tubular segment, the beneficial cooling effect on aerosol nucleation under these conditions is expected to be maximized.

The equivalent inner diameter of a hollow tubular segment is preferably substantially constant along the length of the hollow tubular segment. However, in some embodiments, the cross-sectional surface area of a hollow tubular segment may vary along the length of the hollow tubular segment. In such embodiments, the equivalent inner diameter is measured at the location of the ventilation zone.

As briefly described above, aerosol-generating articles according to the present invention include a ventilation zone located along the hollow tubular segment. Preferably, the ventilation zone is provided less than about 18 millimeters from the upstream end of the hollow tubular segment. Preferably, the distance between the ventilation zone and the upstream end of the hollow tubular segment is less than about 15 millimeters. Even more preferably, the distance between the ventilation zone and the upstream end of the hollow tubular segment is less than about 10 millimeters.

Additionally or alternatively, it is preferred that the distance between the ventilation zone and the upstream end of the hollow tubular segment be at least 2 millimeters. More preferably, the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least about 4 millimeters. Even more preferably, the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least about 6 millimeters.

In embodiments of the aerosol-generating article according to the present invention that include a mouthpiece, the ventilation zone is preferably provided at a position along the hollow tubular segment that is at least 2 millimeters from the upstream end of the mouthpiece. Preferably, the ventilation zone is provided at a position along the hollow tubular segment that is at least 4 millimeters from the upstream end of the mouthpiece. Even more preferably, the ventilation zone is provided at a position along the hollow tubular segment that is at least 6 millimeters from the upstream end of the mouthpiece.

When the mixture of air and aerosol particles flowing through the aerosol-generating article reaches the ventilation zone, ambient air drawn into the hollow tubular segment through the ventilation zone mixes with the aerosol. This rapidly reduces the temperature of the aerosol mixture while partially diluting the mixture of air and aerosol particles. However, by providing the ventilation zone at a distance from the upstream end of the mouthpiece segment within the aforementioned range, a cooling chamber is effectively provided immediately upstream of the mouthpiece, where nucleation and aerosol particle growth can be favored. In this way, the dilution effect of the flowing air entering the hollow tubular segment is at least partially offset, which advantageously allows for the provision of aerosol delivery levels satisfactory to consumers.

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

In particularly preferred embodiments, the ratio of the distance between the ventilation zone and the upstream end of the hollow tubular segment to the equivalent inner diameter of the hollow tubular segment 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.

Preferably, the ventilation zone is provided at a position along the hollow tubular segment at least 10 millimeters from the downstream end of the aerosol-generating article. More preferably, the ventilation zone is provided at a position along the hollow tubular segment at least 12 millimeters from the downstream end of the aerosol-generating article. Even more preferably, the ventilation zone is provided at a position along the hollow tubular segment at least 15 millimeters from the downstream end of the aerosol-generating article. This is advantageous in ensuring that the ventilation zone is not blocked by the consumer's lips during use.

Additionally or alternatively, the ventilation zone is preferably located along the hollow tubular segment less than 25 millimeters from the downstream end of the aerosol-generating article. More preferably, the ventilation zone is located along the hollow tubular segment less than 20 millimeters from the downstream end of the aerosol-generating article. This advantageously ensures that, in use, when the aerosol-generating article is received within the heating chamber of an electrically heated aerosol generating device, the ventilation zone is effectively located along the hollow tubular segment that projects outside the heating chamber so that cool ambient air can be easily drawn into the hollow tubular segment.

In some preferred embodiments, the ventilation zone is provided along the hollow tubular segment from about 10 millimeters to about 25 millimeters from the downstream end of the aerosol-generating device, more preferably from about 12 millimeters to about 20 millimeters from the downstream end of the aerosol-generating device. In an exemplary embodiment, the ventilation zone is provided along the hollow tubular segment from about 18 millimeters from the downstream end of the aerosol-generating device. In another exemplary embodiment, the ventilation zone is provided along the hollow tubular segment from about 13 millimeters from the downstream end of the aerosol-generating device.

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

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

Without wishing to be bound by theory, the inventors have found that the temperature drop caused by admitting cooler ambient air into the hollow tubular segment through the ventilation zone can have a beneficial effect on aerosol particle nucleation and growth.

The formation of aerosols from gaseous mixtures containing various chemical species depends on a delicate interplay between nucleation, evaporation, condensation, and fusion, which accounts for changes in vapor concentration, temperature, and velocity fields. So-called traditional nucleation theory is based on the assumption that a fraction of molecules in the gas phase are large enough to remain coherent for a long time with a sufficient probability (e.g., 1/2 probability). These molecules represent a type of critical, threshold molecular cluster among transient molecular aggregates, meaning that smaller molecular clusters generally tend to break down into the gas phase more quickly, while larger clusters generally tend to grow more easily. These critical clusters are identified as primary nucleation cores from which droplets are expected to grow due to the condensation of molecules from the vapor. Freshly nucleated, raw droplets are assumed to emerge with a specific original diameter and subsequently grow by several sizes. This can be facilitated and enhanced by the rapid cooling of the surrounding vapor, which induces condensation. In this regard, it is helpful to remember 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 the same.

In this scenario, the temperature and rate of cooling can play an important role in determining how the system responds, although fusion phenomena may add further complexity. In general, different cooling rates can lead to significantly different temperature behaviors with respect to the formation of the liquid phase (droplets), as the nucleation process is generally nonlinear. Without being bound by theory, it is hypothesized that cooling causes a sudden increase in the number of droplets condensing, after which this growth can increase strongly in a short period of time (burst nucleation). This burst nucleation appears to be more significant at low temperatures. Furthermore, a high cooling rate may favor the onset of early nucleation. In contrast, a reduction in the cooling rate appears to have a favorable effect on the final size reached by the aerosol droplets.

Thus, the rapid cooling induced by admitting ambient air into the hollow tubular segment through the ventilation zone can be advantageously used to favor the nucleation and growth of aerosol droplets. However, at the same time, admitting ambient air into the hollow tubular segment has the direct drawback of diluting the aerosol stream delivered to the consumer.

Surprisingly, the inventors have found that the dilution effect on the aerosol, which can be assessed in particular by measuring the effect on the delivery of glycerin contained in the aerosol former, is advantageously minimized when the aeration level is between 30 percent and 50 percent. In particular, aeration levels of between 35 percent and 42 percent have been found to lead to particularly satisfactory glycerin delivery values.

Furthermore, the inventors have discovered that in an aerosol-generating article according to the present invention, the cooling and dilution effect caused by the flowing air at locations along the conduit defined by the hollow tubular segment described above has a surprising reducing effect on the generation and delivery of phenol-containing species.

The ventilation zone may include one or more rows of perforations formed through the peripheral wall of the hollow tubular segment. Preferably, the ventilation zone includes only one row of perforations. This is understood to be advantageous in that it can further enhance aerosol nucleation by concentrating the cooling effect provided by the ventilation on the short portion of the cavity defined by the hollow tubular segment. This is because the faster and more dramatic cooling of the volatilized species stream is expected to be particularly favorable to the formation of new nuclei of aerosol particles.

The one or more rows of perforations are preferably arranged circumferentially around the wall of the hollow tube. When the ventilation zone includes two or more rows of perforations formed through the peripheral wall of the hollow tubular segment, the rows are longitudinally spaced apart from one another along the hollow tubular segment. By way of example, adjacent rows of perforations may be longitudinally spaced apart from one another by a distance of approximately 0.25 millimeters to 0.75 millimeters.

Preferably, the equivalent diameter of at least one of the ventilation perforations is at least about 100 micrometers. Preferably, the equivalent diameter of at least one of the ventilation perforations is at least about 150 micrometers. Even more preferably, the equivalent diameter of at least one of the ventilation perforations is at least about 200 micrometers. Additionally or alternatively, it is preferred that the equivalent diameter of at least one of the ventilation perforations is less than about 500 micrometers. More preferably, the equivalent diameter of at least one of the ventilation perforations is less than about 450 micrometers. Even more preferably, the equivalent diameter of at least one of the ventilation perforations is less than about 400 micrometers. The term "equivalent diameter," as used herein, means 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 may have any suitable shape. However, circular ventilation perforations are preferred.

The ventilation perforations may be of uniform size. Alternatively, the ventilation perforations may vary in size. By varying the number and size of the ventilation perforations, it is possible to adjust the amount of ambient air that enters the hollow tubular segment when a consumer draws on the mouth end of the aerosol-generating article during use. Advantageously, it is therefore possible to adjust the level of ventilation in the aerosol-generating article.

The vent perforations may be formed using any suitable technique, such as laser techniques, mechanical perforation of the hollow tubular segment as part of the aerosol-generating article, or pre-perforation of the hollow tubular segment before it is combined with other elements to form the aerosol-generating article. Preferably, the vent perforations are formed by online laser perforation.

The length of the hollow tubular segment is preferably at least about 10 millimeters. More preferably, the length of the hollow tubular segment is at least about 15 millimeters. Additionally or alternatively, the length of the hollow tubular segment is preferably less than about 30 millimeters. More preferably, the length of the hollow tubular segment is less than about 25 millimeters. Even more preferably, the length of the hollow tubular segment is less than about 20 millimeters. In some preferred embodiments, the length of the hollow tubular segment is between about 10 millimeters and about 30 millimeters, more preferably between about 12 millimeters and about 25 millimeters, and even more preferably between about 15 millimeters and about 20 millimeters. By way of example, in a particularly preferred embodiment, the length of the hollow tubular segment is about 18 millimeters. In another particularly preferred embodiment, the length of the hollow tubular segment is about 13 millimeters.

The total length of an aerosol-generating article according to the present invention is preferably at least about 40 millimeters. Additionally or alternatively, the total length of an 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 from about 40 millimeters to about 70 millimeters. In an exemplary embodiment, the total length of the aerosol-generating article is about 45 millimeters.

The hollow tubular segment is preferably formed from a substantially impermeable material. Thus, air and aerosol particles drawn through the hollow tubular segment are forced to flow through the hollow tubular segment from its upstream end to its downstream end, but are unable to flow across the peripheral wall of the hollow tubular element.

In some embodiments, the hollow tubular segment includes a wrapper, which also surrounds the rod. If a mouthpiece segment is present, the wrapper also surrounds the mouthpiece segment. In practice, a wrapper having a thickness within the above ranges is used to surround and connect the rod of the aerosol-generating substrate (and optionally the mouthpiece segment), with the wrapper effectively forming the peripheral wall of the hollow tubular element.

By way of example, the combination of the wrapper and mouthpiece segment connecting such rods may have a basis weight of at least about 70 grams per square meter (gsm). Preferably, the combination of the wrapper and mouthpiece segment connecting such rods has a basis weight of at least about 80 grams per square meter, and more preferably at least about 90 grams per square meter. In particularly preferred embodiments, the combination of the wrapper and mouthpiece segment connecting such rods has a basis weight of at least about 110 grams per square meter, and more preferably at least about 130 grams per square meter.

In other embodiments, the hollow tubular segment comprises a tube formed from a polymeric or cellulosic material, and the heated aerosol-generating article further comprises a wrapper surrounding the rod, the tube, and any mouthpiece segments. By way of example, the cellulosic material may comprise paper or cardboard, or a mixture thereof.

As an example, the hollow tubular segment may include a tube formed from extruded plastic tubing. Alternatively, the hollow tubular segment may include a tube formed from multiple overlapping paper layers, such as multiple parallel wound paper layers or multiple spirally wound paper layers. Forming the tube from multiple overlapping paper layers may help further improve resistance to collapse or deformation. Preferably, the tube includes two or more paper layers. Alternatively, or additionally, the tube preferably includes fewer than 11 paper layers.

One such tube can be made air-impermeable by using substantially air-impermeable paper. The term "substantially air-impermeable paper," as used herein, is used to mean 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 in accordance with ISO 2965:2009. Alternatively, adjacent paper layers within the tube can be held together with an adhesive that provides sealing properties to the tube.

Suitable materials for forming the tube are well 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 grams per square meter), polymeric films such as cellulosic films, and cardboard.

In an aerosol-generating article according to the present invention, the hollow tubular segments are substantially empty and therefore contribute substantially only a small amount to the overall RTD, so the overall RTD of the article depends essentially on the RTD of the rod and, if present, the RTD of the mouthpiece. In practice, the hollow tubular segments may be adapted to generate an RTD in the range of approximately 1 millimeter _{of H2O} (approximately 10 Pa) to approximately 20 millimeters of _H2O (approximately 200 Pa). Preferably, the hollow tubular segments are adapted to generate an RTD of approximately 2 millimeters of _H2O (approximately 20 Pa) to approximately 10 millimeters of _H2O (approximately 100 Pa).

Preferably, the aerosol-generating article has an overall RTD of less than about 90 millimeters _H2O (about 900 Pa). More preferably, the aerosol-generating article has an overall RTD of less than about 80 millimeters _H2O (about 800 Pa). Even more preferably, the aerosol-generating article has an overall RTD of less than about 70 millimeters _H2O (about 700 Pa).

Additionally or alternatively, the aerosol-generating article preferably has an overall RTD of at least about 30 millimeters _H2O (about 300 Pa) _. More preferably, the aerosol-generating article has an overall RTD of at least about 40 millimeters H2O (about 400 Pa). Even more preferably, the aerosol-generating article has an overall RTD of at least about 50 millimeters _H2O (about 500 Pa).

The RTD of an aerosol-generating article can be evaluated as the negative pressure applied to the downstream end of the article (or the mouthpiece segment, if present) under test conditions defined in ISO 3402 to maintain a stable airflow rate of 17.5 ml/s through the mouthpiece segment. The above RTD values are intended to be measured on the aerosol-generating article itself (i.e., before inserting the article into an aerosol-generating device), without blocking any ventilation zone perforations.

If desired or necessary, the length and density (denier per filament count) of the filtration material of the optional mouthpiece may be adjusted, for example, to achieve a sufficiently high RTD of the aerosol-generating article. Additionally or alternatively, an additional filter section may be included in the aerosol-generating article. By way of example, such an additional filter section may be included between the rod and the hollow tubular segment of the aerosol-generating substrate. Preferably, such an additional filter section comprises a filtration material such as, for example, cellulose acetate. The length of the additional filter section is preferably from about 4 millimeters to about 8 millimeters, and more preferably from about 5 millimeters to about 7 millimeters.

In some embodiments, an aerosol-generating article according to the present invention may include an additional support element disposed between and longitudinally aligned with the rod and hollow tubular segment of the aerosol-generating substrate. More particularly, the support element is preferably provided immediately downstream of the rod and immediately upstream of the hollow tubular element.

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

The support element preferably has an outer diameter approximately equal to the outer diameter of the aerosol-generating article. The support element may have an outer diameter of about 5 millimeters to about 12 millimeters, for example, about 5 millimeters to about 10 millimeters, or about 6 millimeters to about 8 millimeters. In a preferred embodiment, the support element has an outer diameter of about 7.2 millimeters.

The peripheral wall of the support element may have a thickness of at least 1 millimeter, preferably at least about 1.5 millimeters, and more preferably at least about 2 millimeters.

The support element can have a length of about 5 millimeters to about 15 millimeters. In one preferred embodiment, the support element has a length of about 8 millimeters.

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 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. In addition, application of force 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 result in uneven and inefficient heating of the aerosol-forming substrate of the aerosol-generating article. Advantageously, the support element is 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.

The distance between the ventilation zone and the upstream end of the aerosol-generating article is preferably less than about 50 millimeters. More preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 45 millimeters. Even more preferably, the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 40 millimeters.

Additionally or alternatively, it is preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article be at least about 12 millimeters. It is even more preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article be at least about 15 millimeters. It is even more preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article be at least about 20 millimeters. In a particularly preferred embodiment, it is preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article be at least about 25 millimeters.

The distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is typically at least about 2 millimeters. Preferably, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is at least about 4 millimeters. More preferably, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is at least about 5 millimeters. Even more preferably, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is at least about 10 millimeters. In some particularly preferred embodiments, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod may be at least about 15 millimeters.

Additionally or alternatively, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is preferably less than about 35 millimeters. More preferably, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is less than about 30 millimeters. Even more preferably, the distance between the ventilation zone and the downstream end of the aerosol-generating substrate rod is less than about 25 millimeters.

In practice, the ventilation zone divides the cavity defined internally by the hollow tubular segment into an upstream sub-cavity extending longitudinally from the upstream end of the hollow tubular segment to the location of the ventilation zone, and a downstream sub-cavity extending longitudinally from the location of the ventilation zone to the downstream end of the hollow tubular segment. Without being bound by theory, it is understood that in the upstream sub-cavity, volatilized species of the aerosol stream traveling along the hollow tubular segment slowly cool by donating a portion of their heat to the surrounding walls of the hollow tubular segment, and aerosol particles begin to nucleate. Meanwhile, in the downstream sub-cavity, the aerosol stream and ventilation air rapidly mix, which rapidly cools the volatilized species of the aerosol stream and favors the nucleation of new aerosol particles and the growth of existing aerosol particles as the aerosol travels toward the mouth end of the article.

The ratio of the length of the upstream recess to the length of the downstream recess is preferably less than 1.5. It is more preferable that the ratio of the length of the upstream recess to the length of the downstream recess is less than 1. It is even more preferable that the ratio of the length of the upstream recess to the length of the downstream recess is less than 0.67.

Additionally or alternatively, it is preferred that the ratio between the length of the upstream recess and the length of the downstream recess be at least about 0.15. It is more preferred that the ratio between the length of the upstream recess and the length of the downstream recess be at least about 0.2. It is even more preferred that the ratio between the length of the upstream recess and the length of the downstream recess be at least about 0.35.

Similarly, the ventilation zone divides the aerosol-generating article into two sections, one upstream and one downstream of the location of the ventilation zone.

It is preferred that 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. It is more preferred that 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. It is even more preferred that 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.

Additionally or alternatively, it is preferred that 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 at least about 0.25. It is more preferred that 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 at least about 0.33. It is even more preferred that 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 at least about 0.5.

Aerosol-generating articles according to the present invention advantageously facilitate adjustment and control of the overall RTD of the article. This is because the overall RTD of the article depends on the RTDs of a finite number of components, and the provision of ventilation zones contributes to a reduction in the overall RTD of the article. Therefore, RTD variation between aerosol-generating articles can be advantageously reduced.

Thus, the present invention may also provide a pack containing 10 or more aerosol-generating articles, as described above, wherein the difference between the RTD of the aerosol-generating article having the highest RTD among the at least 10 aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD among the at least 10 aerosol-generating articles is less than 10 mm _H2O (about 100 Pascals). In such a pack, the difference between the RTD of the aerosol-generating article having the highest RTD among the at least 10 aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD among the at least 10 aerosol-generating articles is preferably 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).

The present invention will now be further described with reference to the accompanying drawings.

FIG. 1 shows a schematic cross-sectional side view of an aerosol-generating article according to the present invention. FIG. 2 shows a schematic cross-sectional side view of another embodiment of an aerosol-generating article according to the present invention. FIG. 3 shows a schematic cross-sectional side view of a further embodiment of an aerosol-generating article according to the present invention.

The aerosol-generating article 10 shown in FIG. 1 includes a rod of aerosol-generating substrate 12, a hollow cellulose acetate tube 14, a hollow tubular segment 16, and a mouthpiece segment 18. These four elements are arranged longitudinally end-to-end and surrounded by an outer wrapper 20 to form the aerosol-generating article 10. The aerosol-generating article 10 has a mouth end 22 and a distal end 24 located at the opposite end of the article from the mouth end 22. The aerosol-generating article 10 shown in FIG. 1 is particularly suitable for use in an electrically operated aerosol generating device that includes a heater for heating the rod of aerosol-generating substrate.

The rod of aerosol-generating substrate 12 has a length of approximately 12 millimeters and a diameter of approximately 7 millimeters. The rod 12 is cylindrical in shape and has a substantially circular cross-section. The rod 12 comprises an assembly of sheets of homogenized tobacco material. The sheets of homogenized tobacco material contain 10 weight percent glycerin on a dry basis. The hollow cellulose acetate tube 14 has a length of approximately 8 millimeters and a thickness of 1 millimeter.

The mouthpiece segment 18 includes a plug of cellulose acetate tow having 8 denier per filament and a length of approximately 7 millimeters.

The hollow tubular segment 14 is provided as a cylindrical tube having a length of approximately 18 millimeters, with a tube wall thickness of approximately 100 micrometers.

More specifically, the hollow tubular segment 16 may be formed, for example, from paper having a basis weight of 110 gsm and has a weight of 45 milligrams (i.e., 2.5 milligrams per millimeter of length). The equivalent inner diameter of the hollow tubular segment 16 is approximately 7 millimeters. Thus, the volume of the cavity defined internally by the hollow tubular segment 16 is approximately 693 cubic millimeters. Therefore, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment 16 is approximately 0.065.

The aerosol-generating article 10 includes a ventilation zone 26 located approximately 5 millimeters from the upstream end of the mouthpiece segment 18. The ventilation zone 26 is therefore approximately 12 millimeters from the downstream end of the aerosol-generating article and approximately 13 millimeters from the upstream end of the hollow tubular segment. The ventilation zone 26 is therefore approximately 21 millimeters from the downstream end of the rod 12.

Figure 2 illustrates another embodiment of an aerosol-generating article according to the present invention. The aerosol-generating article 30 of Figure 2 has the same structure as the aerosol-generating article 10 of Figure 1, differing substantially only in the lengths of certain components, and will therefore be described below to the extent that it differs from the aerosol-generating article 10. Hereinafter, the same reference numerals will be used, whenever possible, for corresponding components having the same structure or functional features.

In the aerosol-generating article 30 of FIG. 2, the rod 12 and hollow cellulose acetate tube 14 have the same length as the aerosol-generating article 10 of FIG. 1. However, the mouthpiece segment includes a plug of cellulose acetate tow having 11 denier per filament and a length of approximately 12 millimeters, and the hollow tubular segment 14 has a length of approximately 13 millimeters. A ventilation zone 26 is provided approximately 6 millimeters from the upstream end of the mouthpiece segment 18 and approximately 7 millimeters from the upstream end of the hollow tubular segment. Thus, the ventilation zone 26 is approximately 15 millimeters from the downstream end of the rod 12.

In the embodiment of FIG. 2, the hollow tubular segment 16 may be provided, for example, as a cylindrical tube of cellulose acetate having a length of approximately 18 millimeters and a peripheral wall thickness of approximately 1 millimeter, weighing 171 milligrams (i.e., 9.5 milligrams per millimeter of length).

The equivalent internal diameter of the hollow tubular segment 16 may be approximately 5.3 millimeters. Accordingly, the volume of the cavity defined internally by the hollow tubular segment 16 is approximately 397 cubic millimeters. Therefore, the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment 16 is approximately 0.43. Figure 3 illustrates yet another embodiment of an aerosol-generating article according to the present invention. The aerosol-generating article 40 of Figure 3 is structurally different from the aerosol-generating article 10 of Figure 1 and the aerosol-generating article 30 of Figure 2 in that it does not include a hollow cellulose acetate tube as a support element. Therefore, the lengths of the three main components are also different. Hereinafter, the same reference numerals will be used whenever possible for corresponding components having the same structure or functional features.

In the aerosol-generating article 40 of FIG. 3, the rod 12 has a length of approximately 12 millimeters, the hollow tubular segment 14 has a length of approximately 26 millimeters, and the mouthpiece segment 18 includes a plug of cellulose acetate tow having a length of approximately 12 millimeters and an 11 denier per filament. A ventilation zone 26 is provided approximately 5 millimeters from the upstream end of the mouthpiece segment 18 and approximately 21 millimeters from the upstream end of the hollow tubular segment, which in this embodiment coincides with the downstream end of the rod 12.

The following examples record experimental results obtained during testing conducted on specific embodiments of aerosol-generating articles according to the present invention. The conditions and smoking machine specifications for smoking are set to ISO standard 3308 (ISO 3308:2000). The ambient air for conditioning and testing is set to ISO standard 3402.

Example 1: This experiment is conducted to evaluate the effect of incorporating a hollow tubular segment in accordance with the present invention, with ventilation zones provided at locations along the hollow tubular segment. The experiment investigates the effect of ventilation level on the delivery of nicotine and an aerosol former (glycerin). Comparative measurements using a reference aerosol-generating article without ventilation are also provided.

Materials and Methods Article A is an aerosol-generating article formed from: a rod of aerosol-generating substrate comprising a conglomerate of sheets of homogenized tobacco material and approximately 18 percent glycerin on a dry weight basis, the rod having a length of 12 millimeters; a support element in the form of a hollow cellulose acetate tube aligned with the rod and located immediately downstream thereof, the support element having a length of 8 millimeters; a hollow tubular segment in the form of a cardboard tube aligned with the rod and located immediately downstream thereof, the hollow tubular segment having a length of 13 millimeters; and a mouthpiece segment of filtration material aligned with the hollow tubular segment and located immediately downstream thereof, the mouthpiece having a length of 12 millimeters. A ventilation zone is provided along the hollow tubular segment 18 millimeters from the downstream end of the mouthpiece segment. The ventilation level of aerosol-generating article A is 30 percent.

Article B is a reference aerosol-generating article that has the same structure as Article A but does not include a ventilation zone. Therefore, the ventilation level of Aerosol-generating Article B is 0 percent.

Nicotine and glycerin delivery was measured by gas chromatography/time-of-flight mass spectrometry (GC/MS-TOF) of nicotine and glycerin collected on Cambridge filter pads. Electrophoresis was performed as described in Example 1.

Results Table 1 below shows the average delivery of nicotine and glycerin from Article A and Article B.
Table 1. Effect of aeration level on nicotine and glycerin delivery.

1. An aerosol-generating article for producing an inhalable aerosol upon heating, said aerosol-generating article comprising:
a rod of an aerosol-generating substrate;
a hollow tubular segment located downstream of the rod, the hollow tubular segment being longitudinally aligned with the rod, the hollow tubular segment defining a recess extending entirely from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment;
a ventilation zone located along the hollow tubular segment;
the hollow tubular segment having a length of less than about 25 millimeters;
the aerosol-generating article has a total length of about 40 millimeters to about 70 millimeters;
the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is preferably less than 1 milligram per cubic millimeter;
An aerosol-generating article, wherein the rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol-former content of at least about 10 percent on a dry weight basis.
2. The aerosol-generating article of claim 1, wherein the hollow tubular segment includes a wrapper, the wrapper also surrounding the rod.
3. The aerosol-generating article of claim 1, wherein the hollow tubular segment comprises a tube formed from a polymeric or cellulosic material, and the heated aerosol-generating article further comprises a wrapper surrounding the rod and the tube.
4. The aerosol-generating article according to any one of 1 to 3, wherein the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.2 milligrams per cubic millimeter.
5. An aerosol-generating article according to any one of 1 to 4, wherein the equivalent inner diameter of the hollow tubular segment at said location in the ventilation zone is at least about 5 millimeters.
6. An aerosol-generating article according to any one of 1 to 5, wherein the equivalent inner diameter of the hollow tubular segment at said location in the ventilation zone is less than about 9 millimeters.
7. An aerosol-generating article according to any one of 1 to 6, wherein the hollow tubular segment has a length of at least about 10 millimeters.
8. An aerosol-generating article according to any one of 1 to 7, wherein the ventilation zone divides the cavity into an upstream sub-cavity extending from the upstream end of the hollow tubular segment to said location in the ventilation zone and a downstream sub-cavity extending from said location in the ventilation zone to said downstream end of the hollow tubular segment, and wherein the ratio of the length of the upstream cavity to the length of the downstream cavity is preferably at least about 0.15.
9. An aerosol-generating article according to any one of 1 to 8, wherein the peripheral wall thickness of the hollow tubular segment is less than about 1.5 millimeters.
10. An aerosol-generating article according to any one of 1 to 9, wherein the RTD of the aerosol-generating article is from about 30 millimeters _H2O to about 90 millimeters _H2O .
11. An aerosol-generating article according to any one of 1 to 10, wherein the ratio between the weight of the hollow tubular segment and the volume of the internal cavity defined by the hollow tubular segment is preferably less than 0.5 milligrams per cubic millimeter.
12. An aerosol-generating article according to any one of 1 to 11, having a breathability level of at least about 20 percent.
13. An aerosol-generating article according to any one of 1 to 12, having a breathability level of less than about 50 percent.
14. An aerosol-generating article according to any one of 1 to 13, wherein the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least about 2 millimeters.
15. The aerosol-generating article of any one of 1 to 14, wherein the ratio of the distance between the ventilation zone and the upstream end of the hollow tubular segment to the equivalent inner diameter of the hollow tubular segment at said location in the ventilation zone is less than 4.

Claims (13)

1. An aerosol-generating article for producing an inhalable aerosol upon heating, said aerosol-generating article comprising:
a rod of an aerosol-generating substrate;
a hollow tubular segment located downstream of the rod, the hollow tubular segment being longitudinally aligned with the rod, the hollow tubular segment defining an internal recess extending entirely from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment;
a ventilation zone disposed along the hollow tubular segment;
Including,
the ventilation zone includes one or more rows of perforations formed through a peripheral wall of the hollow tubular segment;
the hollow tubular segment has a length of less than 25 millimeters;
the hollow tubular segment comprises a tube formed from a polymeric or cellulosic material, and the aerosol-generating article further comprises a wrapper surrounding the rod and the tube;
a ratio of the weight of the hollow tubular segment to the volume of the interior cavity defined by the hollow tubular segment is less than 1 milligram per cubic millimeter;
the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least 4 millimeters;
An aerosol-generating article, wherein the rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol-former content of at least 10 percent on a dry weight basis. The aerosol-generating article of claim 1, wherein the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.5 milligrams per cubic millimeter. 3. The aerosol-generating article of claim 1 , wherein the ratio of the weight of the hollow tubular segment to the volume of the internal cavity defined by the hollow tubular segment is less than 0.2 milligrams per cubic millimeter. 4. The aerosol-generating article of claim 1 , wherein the equivalent inner diameter of the hollow tubular segment is at least 5 millimeters at the location of the ventilation zone. 5. The aerosol-generating article of claim 1 , wherein the equivalent inner diameter of the hollow tubular segment is at least 6 millimeters at the location of the ventilation zone. 6. An aerosol-generating article according to claim 1 , wherein the peripheral wall thickness of the hollow tubular segment is less than 1.5 millimeters. 7. The aerosol-generating article of claim 1, having a breathability level of at least 20 percent. 8. The aerosol-generating article of claim 1 , wherein the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least 6 millimeters. 9. An aerosol-generating article according to any one of claims 1 to 8, wherein the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than 45 millimeters. 10. An aerosol-generating article according to any one of claims 1 to 9, wherein the distance between the ventilation zone and the downstream end of the aerosol-generating article is less than 25 millimeters. The aerosol-generating article described in any one of claims 1 to 10, wherein the ratio of the distance between the ventilation zone and the upstream end of the hollow tubular segment to the equivalent inner diameter of the hollow tubular segment at the location of the ventilation zone is less than 4. 12. The aerosol-generating article according to claim 1 , wherein the outer diameter of the rod of the aerosol-generating substrate is from 6 mm to 8 mm. 13. The aerosol-generating article of claim 1, wherein the ventilation zone comprises two rows of perforations formed through the peripheral wall of the hollow tubular segment, the rows of perforations being spaced apart longitudinally along the hollow tubular segment .