JP7476193B2 - Aerosol-generating article including light hollow segments - Google Patents

Description

The present invention relates to an aerosol-generating article that includes 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, an 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 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 an aerosol-generating article, including, for example, electrically heated aerosol generating devices in which the aerosol is generated by heat transfer from one or more electric heater elements of the aerosol generating device to an aerosol-generating substrate of the heated aerosol-generating article.

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 a longitudinal porosity that allows air to be drawn through the rod. In effect, the folds in the assembly of tobacco material sheets 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. Also, in an alternative embodiment, the rods of WO-A-2011/101164 may 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 the aerosol-generating article to include one or more additional elements assembled with the substrate in the same wrapper for generating an inhalable aerosol upon heating. Examples of such additional elements include mouthpiece filtering segments, support elements adapted to provide structural strength to the aerosol-generating article, cooling elements adapted to favor cooling of the aerosol before it reaches the mouthpiece, and the like. However, while the inclusion of such additional elements has been proposed in view of their beneficial effects, they generally complicate the overall structure of the aerosol-generating article, making it more complicated 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 having simpler structures have been proposed. However, in the absence of certain additional components, such as, for example, aerosol cooling elements, it can be more difficult to manufacture an aerosol-generating article that consistently provides a satisfactory aerosol delivery and RTD to the consumer.

It is therefore desirable to provide an aerosol-generating article that is capable of consistently providing a satisfactory aerosol delivery to the consumer during use. Furthermore, it is desirable to provide an improved aerosol-generating article that has such a satisfactory RTD value. It is equally desirable to provide such an aerosol-generating article that is efficiently and rapidly manufactured, and preferably has 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, an aerosol-generating article for generating an inhalable aerosol upon heating is provided, the aerosol-generating article including a rod of an aerosol-generating substrate and a hollow tubular segment downstream of the rod. The hollow tubular segment is longitudinally aligned with the rod and defines a cavity extending entirely from an upstream end of the hollow tubular segment to a downstream end of the hollow tubular segment. Additionally, the hollow tubular segment has a length of less than about 25 millimeters. The aerosol-generating article further includes 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 the aerosol-generating substrate includes at least an aerosol former, the rod of the aerosol-generating substrate having an aerosol former content of at least about 10 percent on a dry weight basis.

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

A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. Localized heat provided by the flame and oxygen in the air drawn through the cigarette ignites the end of the cigarette and the resulting combustion produces inhalable smoke. In contrast, in heated aerosol-generating articles, the aerosol is generated by heating a flavor-generating substrate (such as tobacco). Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which the aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separated aerosol-forming material. For example, the aerosol-generating article according to the present invention finds particular application in aerosol-generating systems 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 have been 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 an aerosol-generating substrate of an aerosol-generating article to generate an aerosol.

The term "tubular segment" is used herein to mean an elongated element that defines a lumen or airflow passage along its longitudinal axis. In particular, the term "tubular" is used hereinafter for a tubular element that has a substantially cylindrical cross-section and defines at least one airflow conduit that establishes uninterrupted fluid communication between an upstream end of the tubular element and a 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 a 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 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 a tapered section or the like. In embodiments in which 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 taken to be an average value calculated based on several values measured as the minimum 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 permit the passage of fluids, particularly air and smoke, through gaps and 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 walls 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 the tobacco lamina and the tobacco stems. Additionally, the homogenized tobacco material may contain one or more small amounts of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during tobacco processing, handling, and shipping. A sheet of homogenized tobacco material may be produced by casting, extrusion, a papermaking process, or any other suitable process known in the art.

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

The 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 ventilated 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 includes a rod of aerosol-generating substrate and a hollow tubular segment downstream of the rod. These two elements are longitudinally aligned. The rod of aerosol-generating substrate includes 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. Additionally, 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 having a length of less than about 25 millimeters. A venting zone is provided at a location along the hollow tubular segment. Additionally, 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 may be significantly reduced as 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 found that satisfactory cooling of the aerosol stream generated upon heating of the article and drawn through the hollow tubular element is achieved by providing aeration zones at locations along the hollow tubular segment. Furthermore, the inventors have unexpectedly found that it may be possible to offset the effects of increased aerosol dilution caused by admitting ventilation air into the article by utilizing hollow tubular segments having lengths 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., close enough to the heat source and the rod of the aerosol-generating substrate) and achieves dramatic cooling of the aerosol stream, which has a favorable effect on the condensation and nucleation of the aerosol particles. Thus, 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 the article according to the invention, effectively provides a cooling chamber within which the nucleation phenomenon is enhanced by slowing down the flow of the aerosol stream, which may favor condensation of the 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 larger 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 above 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 thus provide a sufficiently long chamber for the aerosol stream to flow through and therefore, during use, allow sufficient time for the temperature of the volatilized species to be reduced and for aerosol particle nucleation to occur. Furthermore, it has been found that relatively short hollow tubular segments in the aerosol-generating article according to the invention allow good aerosol nucleation while at the same time not presenting too large a surface area to the aerosol particles on which they can condense.

In practice, in an aerosol-generating article according to the invention, the cross-sectional surface area of the hollow tubular segment recess may be maximized while at the same time ensuring that the hollow tubular segment has the necessary structural strength to prevent collapse of the aerosol-generating article and provide some support to 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 of the cross-sectional surface area of the hollow tubular segment recess is associated with a reduced velocity of the aerosol flow moving 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 comes into contact with 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 a more controllably localized cooling of the stream of volatilized species.

In fact, the inventors have unexpectedly found how the beneficial effects of enhanced nucleation significantly offset the undesirable effects of dilution such that satisfactory values of aerosol delivery are consistently achieved with the 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 rod of the aerosol-generating substrate 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, since the hollow tubular elements do not substantially contribute to the RTD of the aerosol-generating article, in an aerosol-generating article according to the invention, the overall RTD of the article can advantageously be fine-tuned by adjusting the length and density of the rods of the aerosol-generating substrate, or, in embodiments where a mouthpiece segment is present, the length and density of the segments of filtration material of the mouthpiece segment. This allows aerosol-generating substrates to be consistently and very precisely manufactured with a given RTD to provide a satisfactory level of RTD to the consumer, even in the presence of ventilation.

The aerosol-generating article according to the present invention can be manufactured in a continuous process that can be performed quickly and efficiently, and can be easily manufactured on existing production lines for the manufacture of heated aerosol-generating articles without requiring extensive modification of 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 rod of the aerosol-generating substrate may have a length of about 5 millimeters to about 100 mm. The rod of the aerosol-generating substrate preferably has a length of at least about 5 millimeters, and more preferably has a length of at least about 7 millimeters. Additionally or alternatively, the rod of the aerosol-generating substrate preferably has a length of less than about 80 millimeters, more preferably has a length of less than about 65 millimeters, and even more preferably has a length of less than about 50 millimeters. In a particularly preferred embodiment, the rod of the aerosol-generating substrate has a length of less than about 35 millimeters, more preferably has a length of less than 25 millimeters, and even more preferably has a length of less than about 20 millimeters. In one embodiment, the rod of the aerosol-generating substrate may 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.

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 has 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. The one or more sheets of homogenized tobacco material are preferably textured. As used herein, the term "textured sheet" means a sheet that has been crimped, embossed, debossed, perforated, or otherwise modified. A textured sheet of homogenized tobacco material for use in the present invention may include 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 with 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 present invention. This conveniently facilitates assembly of the crimped sheet of homogenized tobacco material to form a rod. However, it will be appreciated that a 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 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 substantially evenly textured 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 according to the present invention may include a plurality of substantially parallel ridges or corrugations that are substantially evenly 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 percent by weight on a dry weight basis, more preferably at least about 60 percent by weight on a dry weight basis, more preferably at least about 70 percent by weight on a dry weight basis, and most preferably at least about 90 percent by weight on a dry weight basis.

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), or one or more extrinsic binders (i.e., tobacco extrinsic binders), or combinations thereof, to aid in agglomerating particulate tobacco. Alternatively, or in addition, 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 formers, 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 treated by any suitable process known in the art, including, but not limited to, mechanical pulping; refining; chemical pulping; bleaching; sulfate pulping; and combinations thereof.

The sheet or web of homogenized tobacco material preferably 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 is substantially resistant to thermal decomposition at the operating temperature 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, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, triacetate, etc.), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.).

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 include a single aerosol former. Alternatively, the sheet or web of homogenized tobacco material may include 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 about 10 percent to about 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 sheets or webs for use in the aerosol-generating articles of the present invention may be made by methods known in the art, such as the method disclosed in International Patent Application No. WO-A-2012/164009 A2. In one preferred embodiment, the sheets of homogenized tobacco material for use in the aerosol-generating articles are formed from a slurry comprising particulate tobacco, guar gum, cellulose fibers and glycerin by a casting process.

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, and the like.

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 rod of aerosol-generating substrate of the article according to the 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. The wrapper is preferably a paper wrapper.

Aerosol-generating articles according to the invention may optionally include a mouthpiece segment 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, flavorants such as menthol. In some embodiments, the mouthpiece may further include a mouth end recess downstream of the plug of filtration material. As an example, the mouthpiece may include a hollow tube longitudinally aligned with the plug of filtration material and disposed immediately downstream of 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 length of the mouthpiece is preferably 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 length of the mouthpiece is preferably less than 25 millimeters, more preferably less than 20 millimeters, and even more preferably less than 15 millimeters. In some preferred embodiments, the length of the mouthpiece is from about 4 millimeters to about 25 millimeters, and more preferably from about 6 millimeters to about 20 millimeters. In an exemplary embodiment, the length of the mouthpiece is about 7 millimeters. In another exemplary embodiment, the length of the mouthpiece is about 12 millimeters.

In other embodiments, alternatively or additionally, a segment of similar filtration material may be provided at a location 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 the volatilized aerosol components released upon heating of the aerosol-generating substrate accumulate and flow. As briefly mentioned above, this chamber extends longitudinally all the way from the upstream end of the hollow tubular segment to the downstream end of the hollow tubular segment.

Thus, in an aerosol-generating article according to the invention, the hollow tubular segment maintains the rod of aerosol-generating substrate at a predetermined distance from the mouth end of the article and provides an elongated airflow conduit through which aerosol is formed and directed towards the mouth end of the article. In 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 the upstream end is greater than the temperature of the volatilized aerosol components exiting the hollow tubular segment at the downstream end (i.e., the end upstream of the mouthpiece, if a mouthpiece is present).

On the one hand, the hollow tubular segment must 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 the 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 the formation of the aerosol and improve the 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 ranges described above, the volume of the cavity 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 about 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 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 about 0.43 milligrams per cubic millimeter.

The thickness of the peripheral wall of the hollow tubular segment is preferably less than 1.5 millimeters. The thickness of the peripheral wall of the hollow tubular segment is preferably less than 1250 micrometers, more preferably less than 1000 micrometers, and even more preferably less than 900 micrometers. In a particularly preferred embodiment, the thickness of the peripheral wall 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 wishing to be bound by theory, it is believed that by utilizing a hollow tubular segment having a peripheral wall thickness within the above-mentioned range, it is possible to advantageously limit or even substantially prevent 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, it is possible to improve the effect of cooling on the formation of new aerosol particles by providing a more controllably localized cooling of the stream of volatilized species drawn through the hollow tubular segment.

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 defined internally 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 corresponds 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 is less than about 10 millimeters. More preferably, the equivalent inner diameter of the hollow tubular segment is less than about 9.5 millimeters, and even more preferably, is 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 an equivalent inner diameter within the ranges mentioned above, can provide particularly satisfactory aerosol delivery values. Without being bound by theory, it is believed that the aerosol stream flowing along a hollow tubular segment having an equivalent inner diameter within the ranges mentioned above flows at a relatively slow speed as the incoming cooler flowing air stream is received by and mixed 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 the 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 the 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, an aerosol-generating article according to the present invention includes a ventilation zone at a location 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 is at least 2 millimeters. It is more preferred that the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least about 4 millimeters. It is even more preferred that 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 invention that include a mouthpiece, the ventilation zone is preferably provided at a position along the hollow tubular segment at least 2 millimeters from the upstream end of the mouthpiece. The ventilation zone is preferably provided at a position along the hollow tubular segment 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 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, the 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 a ventilation zone at a distance from the upstream end of the mouthpiece segment within the ranges mentioned above, a cooling chamber is effectively provided immediately upstream of the mouthpiece where nucleation and growth of aerosol particles may 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 a satisfactory aerosol delivery level to the consumer.

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 location of the ventilation zone is less than 4. It is preferred that 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 3.5. It is more preferred that 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 3. It is even more preferred that 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 2.5.

In a particularly preferred embodiment, 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 such that cool ambient air can be readily drawn into the hollow tubular segment.

In some preferred embodiments, the ventilation zone is provided along the hollow tubular segment at a position 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 at a position 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 at a position 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 ventilation level of at least about 30 percent. More preferably, the aerosol-generating article has a ventilation level of at least about 35 percent. Additionally or alternatively, the aerosol-generating article preferably has a ventilation level of less than about 60 percent. More preferably, the aerosol-generating article has a ventilation level of less than about 50 percent. In particularly preferred embodiments, the aerosol-generating article has a ventilation level of between about 30 percent and about 60 percent. More preferably, the aerosol-generating article has a ventilation level of between about 35 percent and about 50 percent. In some particularly preferred embodiments, the aerosol-generating article has a ventilation level of about 40 percent.

Without wishing to be bound by theory, the inventors have found that the temperature drop caused by admitting cooler outside air through the ventilation zone into the hollow tubular segment 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, and condensation as well as fusion, which describes the changes in vapor concentration, temperature, and velocity fields. The so-called classical nucleation theory is based on the assumption that a fraction of the molecules in the gas phase are large enough to remain coherent for a long time with a sufficient probability (e.g., 1/2 probability). These molecules represent a certain kind of critical, threshold molecular clusters among the ephemeral molecular aggregates, which means that, in general, smaller molecular clusters tend to break down into the gas phase rather quickly, while larger clusters tend to grow in general. These critical clusters are identified as the main nucleation cores from which droplets are expected to grow due to the condensation of molecules from the vapor. It is assumed that the freshly nucleated raw droplets appear with a certain original diameter and can then grow by several sizes. This can be promoted and enhanced by the fast cooling of the surrounding vapor, which induces the condensation. In this regard, it is useful to keep in mind that evaporation and condensation are two aspects of one and the same mechanism, namely mass transfer between gases and liquids. Evaporation involves a net mass transfer from the droplets to the gas phase, while condensation is a 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 may play an important role in determining how the system responds, although fusion phenomena may add further complexity. In general, different cooling rates may lead to significantly different temperature behaviors in terms of the formation of the liquid phase (droplets) since 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 may increase strongly in a short period of time (burst nucleation). This burst nucleation seems to be more significant at low temperatures. Furthermore, it seems that a high cooling rate may favor the onset of early nucleation. In contrast, a reduction in the cooling rate seems to have a favorable effect on the final size that the aerosol droplets eventually reach.

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 may be assessed in particular by measuring the effect on the delivery of glycerin contained in the aerosol former as an aerosol former, is advantageously minimized when the aeration level is between 30 percent and 50 percent. In particular, it has been found that an aeration level of between 35 percent and 42 percent leads to particularly satisfactory values of glycerin delivery.

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 may further enhance aerosol nucleation by concentrating the cooling effect provided by the ventilation on the short portion of the cavity defined by the hollow tube 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 about 0.25 millimeters to 0.75 millimeters.

Preferably, the equivalent diameter of at least one of the vent perforations is at least about 100 micrometers. Preferably, the equivalent diameter of at least one of the vent perforations is at least about 150 micrometers. Even more preferably, the equivalent diameter of at least one of the vent perforations is at least about 200 micrometers. Additionally or alternatively, it is preferred that the equivalent diameter of at least one of the vent perforations is less than about 500 micrometers. More preferably, the equivalent diameter of at least one of the vent perforations is less than about 450 micrometers. Even more preferably, the equivalent diameter of at least one of the vent 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 vent perforation. The cross-section of the vent perforation may have any suitable shape. However, circular vent 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 outside air that enters the hollow tubular segment when a consumer inhales on the mouth end of the aerosol-generating article during use. Thus, advantageously, it is possible to adjust the level of ventilation of 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 overall length of an aerosol-generating article according to the present invention is preferably at least about 40 millimeters. Additionally or alternatively, the overall 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 overall length of the aerosol-generating article is from about 40 millimeters to about 70 millimeters. In an exemplary embodiment, the overall 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 cannot 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 in effect forming the peripheral wall of the hollow tubular element.

By way of example, the combination of wrapper and mouthpiece segments connecting such rods may have a basis weight of at least about 70 grams per square meter (gsm). Preferably, the combination of wrapper and mouthpiece segments 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 wrapper and mouthpiece segments 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.

By way of example, the hollow tubular segment may include a tube formed from an extruded plastic tube. 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, preferably, the tube includes fewer than 11 paper layers.

One such tube may be air impermeable by using a substantially air impermeable paper. The term "substantially air impermeable paper" as used herein is used to mean a 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, measured according to ISO 2965:2009. Alternatively, adjacent paper layers within the tube may 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 invention, the hollow tubular segment is substantially empty and therefore contributes substantially only insignificantly to the overall RTD, so that the overall RTD of the article depends essentially on the RTD of the rod and, if present, of the mouthpiece. In practice, the hollow tubular segment may be adapted to generate an RTD in the range of approximately 1 millimeter _H2O (about 10 Pa) to approximately 20 millimeter _H2O (about 200 Pa). Preferably, the hollow tubular segment is adapted to generate an RTD of approximately 2 millimeter _H2O (about 20 Pa) to approximately 10 millimeter _H2O (about 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 (of 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 the aerosol generating device), without blocking any ventilation zone perforations.

If desired or necessary, the length and density (denier per filament count) of the optional mouthpiece filtration material may be adjusted, for example, to achieve a sufficiently high RTD of the aerosol-generating article. Additionally or alternatively, additional filter sections may be included in the aerosol-generating article. By way of example, such additional filter sections may be included between the rod and the hollow tubular segment of the aerosol-generating substrate. Such additional filter sections preferably comprise a filtration material such as, for example, cellulose acetate. The length of the additional filter sections 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 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, e.g., 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 may 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.

It is preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 50 millimeters. It is more preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article is less than about 45 millimeters. It is even more preferred that 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 is at least about 12 millimeters. It is more preferred that the distance between the ventilation zone and the upstream end of the aerosol-generating article is 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 is 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 is at least about 25 millimeters.

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

Additionally or alternatively, it is preferred that the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 35 millimeters. It is more preferred that the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 30 millimeters. It is even more preferred that the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 25 millimeters.

In practice, the vent 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 vent zone, and a downstream sub-cavity extending longitudinally from the location of the vent zone to the downstream end of the hollow tubular segment. Without being bound by theory, it is understood that in the upstream sub-cavity, the 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 the vent 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.

It is preferred that the ratio of the length of the upstream recess to the length of the downstream recess is less than 1.5. It is more preferred 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 preferred 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 is 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 is preferably 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 is preferably at least about 0.35.

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

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 preferably 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.

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.

Advantageously, the aerosol-generating article according to the invention allows easy adjustment and control of the overall RTD of the article, since it depends on the RTD of a finite, small number of components, and the provision of a ventilation zone contributes to lowering the overall RTD of the article. Thus, advantageously, RTD variation between aerosol-generating articles can be reduced.

Thus, the present invention may also provide a pack comprising 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.

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 relative to 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 about 12 millimeters and a diameter of about 7 millimeters. The rod 12 is cylindrical in shape and has a substantially circular cross-section. The rod 12 includes an assembly of a sheet of homogenized tobacco material. The sheet of homogenized tobacco material includes 10 weight percent glycerin on a dry basis. The hollow cellulose acetate tube 14 has a length of about 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. Thus, 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 provided 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, and differs from the aerosol-generating article 10 substantially only in the length of certain components, and will be described below insofar as it differs from the aerosol-generating article 10. Hereinafter, the same reference numbers 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 about 12 millimeters, and the hollow tubular segment 14 has a length of about 13 millimeters. The ventilation zone 26 is provided about 6 millimeters from the upstream end of the mouthpiece segment 18 and about 7 millimeters from the upstream end of the hollow tubular segment. Thus, the ventilation zone 26 is about 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 about 18 millimeters and a peripheral wall thickness of about 1 millimeter, weighing 171 milligrams (i.e., 9.5 milligrams/millimeter of length).

The equivalent internal diameter of the hollow tubular segment 16 may be about 5.3 millimeters. The volume of the cavity defined internally by the hollow tubular segment 16 is therefore about 397 cubic millimeters. 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 therefore about 0.43. FIG. 3 illustrates yet another embodiment of an aerosol-generating article according to the present invention. The aerosol-generating article 40 of FIG. 3 is structurally different from the aerosol-generating article 10 of FIG. 1 and the aerosol-generating article 30 of FIG. 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 numbers are used as far as 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 about 12 millimeters, the hollow tubular segment 14 has a length of about 26 millimeters, and the mouthpiece segment 18 includes a plug of cellulose acetate tow having a length of about 12 millimeters and 11 denier per filament. A ventilation zone 26 is provided about 5 millimeters from the upstream end of the mouthpiece segment 18 and about 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 document experimental results obtained during testing conducted on specific embodiments of an aerosol-generating article according to the 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, where ventilation zones are provided at locations along the hollow tubular segment. The experiment investigates the effect of ventilation levels on the delivery of nicotine and an aerosol former (glycerin). Comparative measurements with a reference aerosol generating article without ventilation are also provided.

Materials and Methods Article A is an aerosol-generating article, the aerosol-generating article being formed of a rod of aerosol-generating substrate comprising an assembly of sheets of homogenized tobacco material and about 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 of the rod, 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 of the rod, 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 of the hollow tubular segment, the mouthpiece having a length of 12 millimeters. A ventilation zone is provided along the hollow tubular segment at a position 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. Thus, the ventilation level of Aerosol-generating Article B is 0 percent.

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

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

Claims (15)

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 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 an upstream end of the hollow tubular segment to a downstream end of the hollow tubular segment;
a mouthpiece segment located downstream of the hollow tubular segment, the mouthpiece segment including a plug of filtration material and a mouth-end recess downstream of the plug of filtration material;
a ventilation zone along the hollow tubular segment located less than 20 millimeters from the downstream end of the aerosol-generating article, the ventilation zone including one or more rows of perforations formed through a peripheral wall of the hollow tubular segment, the hollow tubular segment having a length of about 25 millimeters;
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 ;
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 12 percent on a dry weight basis. The aerosol-generating article of claim 1, wherein the hollow tubular segment includes a wrapper, the wrapper also surrounding the rod. 2. The aerosol-generating article of claim 1, wherein 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. 4. 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 . The aerosol-generating article of any one of claims 1 to 4, wherein the equivalent inner diameter of the hollow tubular segment is at least about 5 millimeters at the location of the ventilation zone. The aerosol-generating article of any one of claims 1 to 5, wherein the equivalent inner diameter of the hollow tubular segment is less than about 9 millimeters at the location of the ventilation zone. The aerosol-generating article of any one of claims 1 to 6, wherein the mouthpiece segment includes a mouth-end hollow tube defining a mouth-end recess, the mouth-end hollow tube being longitudinally aligned with and positioned immediately downstream of the plug of filtration material, and the recess being open to the outside environment at the downstream end of the mouthpiece segment and the aerosol-generating article. The aerosol-generating article of any one of claims 1 to 7, wherein the peripheral wall thickness of the hollow tubular segment is less than about 1.5 millimeters. 9. An aerosol-generating article according to any one of claims 1 to 8, wherein the RTD of the aerosol-generating article is from about 30 millimeters _H2O to about 90 millimeters _H2O . 10. An aerosol-generating article according to any one of claims 1 to 9, 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 . The aerosol-generating article of any one of claims 1 to 10, having a breathability level of at least about 20 percent. The aerosol-generating article of any one of claims 1 to 11, wherein the distance between the ventilation zone and the upstream end of the hollow tubular segment is at least about 6 millimeters. The aerosol-generating article according to any one of claims 1 to 12, 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. The aerosol-generating article according to any one of claims 1 to 13, wherein the outer diameter of the rod of the aerosol-generating substrate is from about 6 millimeters to about 8 millimeters. The aerosol-generating article of any one of claims 1 to 14, wherein the ventilation zone includes two rows of perforations formed through the peripheral wall of the hollow tubular segment, the rows of perforations being longitudinally spaced apart from one another along the hollow tubular segment.

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