JP7531493B2 - Aerosol-generating article having vented hollow segments - Patents.com - Google Patents

Description

The present invention relates to an aerosol-generating article comprising an aerosol-generating substrate and 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 a 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 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 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 an alternative embodiment, 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.

The substrate for the heated aerosol-generating article typically further comprises an aerosol former, i.e., a compound or mixture of compounds that facilitates 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, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.).

It is also common for an aerosol-generating article for generating an inhalable aerosol upon heating to include one or more additional elements assembled with the substrate in the same wrapper. Examples of such additional elements include a mouthpiece filtering segment, a support element adapted to impart structural strength to the aerosol-generating article, a cooling element adapted to favor cooling of the aerosol before it reaches the mouthpiece, and the like. However, the inclusion of such additional elements, while proposed in view of their beneficial effects, generally complicates the overall structure of the aerosol-generating article, making it more complicated and expensive to manufacture. In fact, the manufacture of such multi-element aerosol-generating articles typically requires somewhat complicated manufacturing machines and machine combinations.

With this in mind, aerosol-generating articles having simpler structures have also been proposed. However, in the absence of certain additional components, such as aerosol cooling elements, it may be more difficult to manufacture an aerosol-generating article that consistently provides satisfactory aerosol delivery and RTD to the consumer.

It would therefore be desirable to provide an aerosol generating article that is capable of consistently providing a satisfactory aerosol delivery to the consumer during use. It would further be desirable to provide one such improved aerosol generating article that has a satisfactory RTD value. It would also be desirable to provide one such aerosol generating article that can be efficiently and rapidly manufactured, and that 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 when heated is provided, the aerosol-generating article comprising a rod of an aerosol-generating substrate, a mouthpiece segment comprising a plug of filtration material disposed downstream of the rod and longitudinally aligned with the first segment, and a hollow tubular segment at a location between the rod and the mouthpiece segment. The hollow tubular segment is longitudinally aligned with the rod and the mouthpiece segment. Further, the hollow tubular segment defines a cavity that extends all the way to the upstream end of the mouthpiece segment. The aerosol-generating article further comprises a vent zone at a location along the hollow tubular segment. The equivalent inner diameter of the hollow tubular segment at the location of the vent zone is at least about 5 millimeters. The rod of the aerosol-generating substrate comprises 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" is used herein to mean an article in which an aerosol-generating substrate is heated to generate an inhalable aerosol for delivery to a consumer. As used herein, the term "aerosol-generating substrate" means a substrate capable of releasing a volatile compound upon heating to generate an aerosol.

A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. Localized heat provided by the flame and oxygen in the air drawn through the cigarette ignites the end of the cigarette and the resulting combustion produces inhalable smoke. In contrast, in heated aerosol-generating articles, the aerosol is generated by heating a flavor-generating substrate (such as tobacco). Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which the aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separated aerosol-forming material. For example, the aerosol-generating article according to the present invention finds particular application in aerosol-generating systems comprising an electrically heated aerosol generator having an internal heater blade adapted to be inserted into a rod of 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 with reference to a tubular element having a substantially cylindrical cross-section and defining 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 appreciated 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 location 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. Any reference to a "cross section" of an aerosol-generating article or a component of an aerosol-generating article refers to a transverse cross section, unless otherwise specified.

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. In the case of a tubular element having 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 as an average value calculated based on several values measured as the minimum distance between the outer and inner surfaces of the wall at different locations 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 conduits 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" encompasses 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 blades and the tobacco stems. In addition, 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 via 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, a mouthpiece segment comprising a plug of filtration material, and a hollow tubular segment located between the rod and the mouthpiece segment. All three elements are longitudinally aligned. The rod of aerosol-generating substrate contains at least an 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. Further, the hollow tubular segment defines a cavity that extends all the way to the upstream end of the mouthpiece segment, and a ventilation zone is provided at a location along the hollow tubular segment. Additionally, the equivalent inner diameter of the hollow tubular segment is at least about 5 millimeters.

By providing an aerosol-generating article in which a hollow tubular element defining a cavity extending all the way to the upstream end of the mouthpiece segment is disposed between the rod of the aerosol-generating substrate and the mouthpiece, 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 the manufacturing and assembly equipment required to carry out the manufacturing process.

One such aerosol-generating article does not necessarily 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 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. Moreover, the inventors have surprisingly found that it may be possible to counter the effects of increased aerosol dilution caused by admitting ventilation air into the article by utilizing a hollow tubular segment having an equivalent inner diameter of at least about 5 millimeters.

Without wishing to be bound by theory, it is hypothesized that the temperature of the aerosol stream is rapidly reduced by the introduction of ventilation air as the aerosol travels toward the mouthpiece segment, so that the ventilation 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. As a result, the overall ratio of aerosol particle phase to aerosol gas phase may be enhanced as compared to existing non-vented aerosol-generating articles.

At the same time, utilizing hollow tubular elements having an equivalent internal diameter of 5 millimeters or more ensures that the overall internal volume of the hollow tubular element (which is utilized to initiate the aerosol nucleation process as soon as the aerosol components leave the rod of the aerosol-generating substrate) and the cross-sectional surface area of the hollow tubular segment are substantially 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 as well as to 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 larger value of the cross-sectional surface area of the cavity of the hollow tubular segment is associated with a reduced velocity of the aerosol flow moving along the aerosol-generating article, which favors aerosol nucleation. Indeed, without wishing to be bound by theory, by providing a cavity having one of these large volumes, as is the case with the article according to the invention, a cooling chamber is provided that is substantially within the range that favors condensation of aerosol particles upstream of the mouth end of the article, since the nucleation phenomenon is enhanced by slowing down the aerosol flow.

Providing a sufficiently wide tubular cavity downstream of the rod of the aerosol-generating substrate is understood to favor the formation of a sufficient amount of aerosol during use, so that a greater proportion of the generated aerosol particles begin to condense before reaching the mouth end of the article.

Indeed, the inventors have surprisingly found how the beneficial effects of enhanced nucleation significantly counteract the less desirable effects of dilution, such that satisfactory values of aerosol delivery are consistently achieved with the aerosol-generating article according to the 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 total 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, in such aerosol-generating articles, there is little time and space for aerosol formation and for the particulate 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 be advantageously fine-tuned by adjusting the length and density of the rods of the aerosol-generating substrate, or the length and density of the segments of the filtration material of the mouthpiece. This allows aerosol-generating substrates to be consistently and very accurately manufactured with a given RTD, so as to provide a satisfactory level of RTD to the consumer, even in the presence of ventilation.

The aerosol-generating articles according to the present invention can be manufactured in a continuous process that can be carried out efficiently at high speed, and can be conveniently 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 one 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 one 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-generating substrate comprises an assembly of one or more 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 is 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 apart indentations, protrusions, perforations, or combinations thereof. According to one particularly preferred embodiment of the present invention, the rod of the 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 substantially 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 according to the invention. This advantageously facilitates assembly of the crimped sheet of homogenized tobacco material to form a rod. However, it will be appreciated that the crimped sheet of homogenized tobacco material used in the present invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that are disposed at an acute or obtuse angle relative to the cylindrical axis of the rod. In certain embodiments, the sheet of homogenized tobacco material used in the rod of the article of the present invention may be substantially evenly textured across substantially its entire surface. For example, the crimped sheet of homogenized tobacco material used 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 uniformly spaced across the width of the sheet.

The homogenized tobacco material sheets or webs used 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, even 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), 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 or web 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, pectin, and the like), and combinations thereof.

Suitable non-tobacco fibers for inclusion in a sheet or web of homogenized tobacco material for use in an aerosol-generating substrate are well known in the art and include, but are not limited to, cellulose fibers, softwood fibers, hardwood fibers, jute fibers, and combinations thereof. Prior to inclusion in a sheet of homogenized tobacco material for use in an aerosol-generating substrate, the non-tobacco fibers 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 that 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 (such as 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 a preferred embodiment, the sheet of homogenized tobacco material 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 methods disclosed in WO-A-2012/164009 A2. In a 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 in 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 about their longitudinal axes, and the like.

As a further alternative, the rod of aerosol-generating substrate may comprise a non-tobacco-derived nicotine-bearing material, such as a sheet of absorbent non-tobacco material loaded with nicotine (e.g. in the form of a nicotine salt) and an aerosol former. Examples of such rods are described in International Application No. WO-A-2015/052652. Additionally or alternatively, the rod of aerosol-generating substrate may comprise a non-tobacco plant material, such as a flavoured 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. Preferably, the wrapper is a paper wrapper.

The mouthpiece segment comprises a plug of filtration material capable of removing particulate components, gaseous components, or a combination. Suitable filtration materials are known in the art and include, but are not limited to, fibrous filtration materials (e.g., cellulose acetate tow, viscose fibers, polyhydroxyalkanoic acid (PHA) fibers, polylactic acid (PLA) fibers, paper, etc.), adsorbents (e.g., activated alumina, zeolites, molecular sieves, silica gel, etc.), and combinations thereof. In addition, the plug of filtration material may further include one or more aerosol modifiers. Suitable aerosol modifiers are known in the art and include, but are not limited to, flavorants, such as menthol. In some embodiments, the mouthpiece may further include a recess in the mouth end downstream of the plug of filtration material. As an example, the mouthpiece may include a hollow tube disposed in longitudinal alignment with the plug of filtration material and disposed immediately downstream of the plug of filtration material, the hollow tube forming a cavity in the mouth end that is open to the external environment at the downstream end of the mouthpiece and the aerosol-generating article.

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 one exemplary embodiment, the length of the mouthpiece is about 7 millimeters. In another exemplary embodiment, the length of the mouthpiece is about 12 millimeters.

The hollow tubular segment is preferably an annular tube that delimits and defines a cavity within the aerosol-generating article. In effect, the hollow tubular segment provides a chamber in 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 to the upstream end of the mouthpiece. This means that no intermediate elements are provided between the hollow tubular segment and the mouthpiece, and that when the aerosol flowing through the aerosol-generating article reaches the downstream end of the hollow tubular segment, the aerosol flowing through the aerosol-generating article also substantially reaches the upstream end of the mouthpiece. More specifically, the aerosol flowing through the aerosol-generating article generally reaches the upstream end of the segment of filtration material of the mouthpiece.

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 mouthpiece and provides an elongated airflow conduit for forming and directing an aerosol towards the mouthpiece. 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 its upstream end is higher 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).

On the one hand, the hollow tubular segment is required 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 is required to 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 therein by the hollow tubular element is as large as possible, to favor the formation of the aerosol and to enhance the delivery of the aerosol to the consumer.

To meet these requirements, as briefly stated above, the equivalent inner diameter of the hollow tubular segment is at least about 5 millimeters. The term "equivalent inner diameter" is used herein to mean the diameter of a circle having the same surface area as the cross-section of the airflow conduit defined therein by the hollow tubular segment. The cross-section of the airflow conduit may have any suitable shape. However, as briefly stated 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 substantially corresponds to the inner diameter of the cylindrical tube.

More preferably, the equivalent inner diameter of the hollow tubular segment is at least about 5.25 millimeters, and even more 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.

In addition, the equivalent inner diameter of the hollow tubular segment is preferably 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.

The inventors have surprisingly found that an aerosol generating article according to the invention comprising a hollow tubular segment having an equivalent inner diameter within the above-mentioned range is capable of providing particularly satisfactory aerosol delivery values. Without wishing to be bound by theory, it is hypothesized that an aerosol stream flowing along a hollow tubular segment having an equivalent inner diameter falling within the above-mentioned range produces a relatively slow flow as the incoming cooler ventilation air stream is received into and mixed with the aerosol stream. Because the aerosol stream progresses 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.

In a preferred embodiment, the peripheral wall thickness of the hollow tubular segment is less than 1.5 millimeters. More preferably, the peripheral wall thickness of the hollow tubular segment is less than 1250 micrometers, even more preferably, less than 1000 micrometers, and most 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 wishing to be bound by theory, it appears that by utilizing hollow tubular segments having peripheral walls of thickness falling within the above-mentioned ranges, it is possible to advantageously limit or even substantially prevent diffusion of the ventilation air prior to its contact and mixing with the aerosol stream. This is understood to be a further advantageous nucleation phenomenon. Indeed, it is possible to enhance the effect of cooling on the formation of new aerosol particles by providing more controllably localized cooling of the stream of volatilized species drawn through the hollow tubular segments.

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. The ventilation zone is preferably 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.

Preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 2 millimeters from the upstream end of the mouthpiece. Preferably, the ventilation zone is provided at a location 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 location 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, 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. As discussed in more detail below, by providing a ventilation zone at a distance from the upstream end of the mouthpiece segment that falls within the ranges mentioned above, however, a cooling chamber is essentially provided immediately upstream of the mouthpiece, which favors nucleation and growth of aerosol particles. In this way, the dilution effect of the ventilation air entering the hollow tubular segment is at least partially countered, which advantageously allows for the provision of a satisfactory aerosol delivery level for 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 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 location along the hollow tubular segment at least 10 millimeters from the downstream end of the mouthpiece segment. More preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 12 millimeters from the downstream end of the mouthpiece segment. Even more preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 15 millimeters from the downstream end of the mouthpiece segment. 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 mouthpiece segment. More preferably, the ventilation zone is located along the hollow tubular segment less than 20 millimeters from the downstream end of the mouthpiece segment. This advantageously ensures that, in use, when the aerosol generating article is received in the heating chamber of the electrically heated aerosol generating device, the ventilation zone is located substantially along the hollow tubular segment that projects outside the heating chamber such 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 mouthpiece segment, more preferably from about 12 millimeters to about 20 millimeters from the downstream end of the mouthpiece segment. In one exemplary embodiment, the ventilation zone is provided along the hollow tubular segment from about 18 millimeters from the downstream end of the mouthpiece segment. In another exemplary embodiment, the ventilation zone is provided along the hollow tubular segment from about 13 millimeters from the downstream end of the mouthpiece segment.

Aerosol-generating articles may 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 reduction caused by admitting cooler outside 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 even fusion, which accounts for the changes in vapor concentration, temperature and velocity fields. The so-called classical nucleation theory is based on the assumption that a fraction of the molecules in the gas phase are large enough to remain coherent for a long time with a sufficient probability (e.g., 1/2 probability). These molecules represent a kind of critical, threshold molecular clusters in the temporary molecular aggregates, which means that smaller molecular clusters are generally prone to break down into the gas phase rather quickly, while larger clusters are generally prone to growth. These critical clusters are identified as the main nucleation cores from which droplets are expected to grow due to the condensation of molecules from the vapor. It is assumed that freshly nucleated raw droplets appear with a certain original diameter and may then grow by several orders of magnitude. This may be facilitated and enhanced by the rapid cooling of the surrounding vapor, which induces 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 unchanged.

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

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

The inventors have surprisingly found that the dilution effect on the aerosol (which can be assessed, inter alia, by measuring the effect on the delivery of glycerin contained in the aerosol-generating substrate 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.

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

The ventilation zone may comprise one or more rows of perforations formed through the peripheral wall of the hollow tubular segment. Preferably, the ventilation zone comprises only one row of perforations. This is understood to be advantageous in that it may further enhance aerosol nucleation by condensing the cooling effect provided by the ventilation over a short portion of the cavity defined by the hollow tube segment. This is because the faster and more dramatic cooling of the stream of volatilized species 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 comprises 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.

The equivalent diameter of at least one of the vent perforations is preferably at least about 100 micrometers. The equivalent diameter of at least one of the vent perforations is preferably 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, the equivalent diameter of at least one of the vent perforations is preferably 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" is used herein to mean 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 draws on the mouthpiece 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 can be formed using any suitable technique, such as by 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 one 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 one exemplary embodiment, the overall length of the aerosol-generating article is about 45 millimeters.

The hollow tubular segment is preferably formed from a substantially air impermeable material, so that 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 comprises a wrapper, which also surrounds the rod and mouthpiece segments. Indeed, a wrapper having a thickness falling within the above ranges is used to surround and connect the rod and mouthpiece segments of the aerosol-generating substrate, with the wrapper essentially forming the peripheral wall of the hollow tubular element.

As an example, one of these bonding wrappers connecting the rod and the mouthpiece segment may have a basis weight of at least about 70 grams per square meter (gsm). Preferably, one of these bonding wrappers connecting the rod and the mouthpiece segment has a basis weight of at least about 80 grams per square meter, and more preferably has a basis weight of at least about 90 grams per square meter. In particularly preferred embodiments, the bonding wrapper connecting the rod and the mouthpiece segment has a basis weight of at least about 110 grams per square meter, and more preferably has a basis weight of 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 the mouthpiece segment. By way of example, the cellulosic material may include paper or cardboard, or a mixture thereof.

By way of example, the hollow tubular segment may comprise a tube formed from an extruded plastic tube. Alternatively, the hollow tubular segment may comprise 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 can help to further improve resistance to collapse or deformation. Preferably, the tube comprises two or more paper layers. Alternatively or additionally, preferably, the tube comprises fewer than 11 paper layers.

One such tube may be made to be air impermeable by using a substantially air impermeable paper. The term "substantially air impermeable paper" is used herein 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, as measured according to ISO 2965:2009. Alternatively, adjacent layers of paper in the tube may be held together with an adhesive that imparts 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 some embodiments, 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 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.

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 0.25 milligrams per 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 0.2 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 0.1 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 that falls 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 substantially spaced from the mouthpiece.

In one exemplary embodiment, the hollow tubular segment has an equivalent inner diameter of 7 millimeters and is formed from a wrapper having a basis weight of 110 gsm, with a weight of 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.

In an aerosol-generating article according to the invention, the overall RTD of the article depends essentially on the RTD of the rod and the RTD of the mouthpiece, since the hollow tubular segment is substantially empty and therefore only contributes substantially insignificantly to the overall RTD. In practice, the hollow tubular segment may be adapted to generate an RTD in the range of approximately 0 millimeters _H2O (about 00 Pa) to approximately 20 millimeters _H2O (about 200 Pa). Preferably, the hollow tubular segment is adapted to generate an RTD of approximately 0 millimeters _H2O (about 00 Pa) to approximately 10 millimeters _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 may be evaluated as the negative pressure that must be applied to the downstream end of the mouthpiece to maintain a stable volumetric flow rate of 17.5 ml/s of air through the mouthpiece under test conditions as defined in ISO 3402. The RTD values listed above are intended to be measured on the aerosol-generating article on its own (i.e., before inserting the article into an aerosol generating device), without blocking any ventilation zone perforations.

For example, the length and density (denier count per filament) of the filtration material of the mouthpiece may be adjusted if desired or necessary 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, the aerosol-generating article according to the invention may comprise an additional support element disposed between and longitudinally aligned with the rod and the 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 one 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 be required to apply some force to overcome the resistance of the aerosol-generating 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, the 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 lead to uneven and inefficient heating of the aerosol-generating substrate of the aerosol-generating article. The support element is advantageously configured to resist downstream movement of the aerosol-forming substrate during insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article.

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 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 preferably at least about 2 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. More preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 30 millimeters. Even more preferably, the distance between the ventilation zone and the downstream end of the rod of the aerosol-generating substrate is less than about 25 millimeters.

In effect, 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 wishing to be bound by theory, it is understood that in the upstream sub-cavity, the volatilized species of the aerosol stream travel along the hollow tubular segment and slowly cool by ceding part of their heat to the peripheral walls of the hollow tubular segment, and therefore aerosol particles begin to nucleate. On the other hand, in the downstream sub-cavity, the aerosol stream and the ventilation air are rapidly mixed, which rapidly cools the volatilized species of the aerosol stream and therefore favors the nucleation of new aerosol particles and the growth of existing aerosol particles as the aerosol travels towards the mouthpiece.

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

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

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.

In an aerosol-generating article according to the invention, it is advantageously simple to adjust and control the overall RTD of the article. This is because the overall RTD of the article depends on the RTD of a finite number of components, and the provision of a ventilation zone contributes to lowering the overall RTD of the article. Thus, advantageously, there is the potential to reduce variability in RTD between aerosol-generating articles.

As a result, the present invention may also provide a pack comprising ten or more aerosol-generating articles as described above, wherein the difference between the RTD of the aerosol-generating article having the highest RTD among the at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD among the at least ten aerosol-generating articles is less than ₁₀ mmH2O (about 100 Pascals). In one such pack, the difference between the RTD of the aerosol-generating article having the highest RTD among the at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD among the at least ten aerosol-generating articles is preferably less than 9 _mmH2O (about 90 Pascals), more preferably less than ₈ mmH2O (about 80 Pascals), and even more preferably less than ₇ mmH2O (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 end-to-end in longitudinal alignment 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 an upstream distal end 24 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 aerosol-generating substrate rod 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 comprises a plug of cellulose acetate tow with 8 denier per filament and has a length of approximately 7 millimeters.

The hollow tubular segment 16 is provided as a cylindrical tube having a length of approximately 18 mm and 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 about 7 millimeters. The volume of the cavity defined internally by the hollow tubular segment 16 is therefore about 693 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 0.065. The aerosol-generating article 10 includes a ventilation zone 26 provided about 5 millimeters from the upstream end of the mouthpiece segment 18. The ventilation zone 26 is therefore about 12 millimeters from the downstream end of the aerosol-generating article and about 13 millimeters from the upstream end of the hollow tubular segment.

Therefore, the ventilation zone 26 is 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 will be described below insofar as it differs from the aerosol-generating article 10 substantially only in the length of certain components. In the following, the same reference numbers will be used as far as possible for corresponding components having the same structure or functional action.

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 comprises a plug of 11 denier cellulose acetate tow per filament and has a length of about 12 millimeters, and the hollow tubular segment 14 has a length of about 13 millimeters. A 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 inner 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. Figure 3 illustrates yet another embodiment of an aerosol-generating article according to the 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. As a result, the lengths of the three main components are also different. In the following, the same reference numbers are used as far as possible for corresponding components having the same structure or functional action.

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 comprises a plug of 11 denier cellulose acetate tow per filament and has a length of about 12 millimeters. The 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 tests performed on specific embodiments of an aerosol-generating article according to the invention. The conditions for smoking and the specifications of the smoking machine are presented in ISO standard 3308 (ISO 3308:2000). The ambient air for conditioning and testing is presented in ISO standard 3402.

Example 1
This experiment is conducted to evaluate the effect of incorporating a hollow tubular segment in which ventilation zones are provided at locations along the hollow tubular segment in accordance with the present invention. 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 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 and 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 and immediately downstream of the rod, the hollow tubular segment having a length of 13 millimeters, and a mouthpiece segment of filtration material aligned with and 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 location 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 have a ventilation zone. Therefore, 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) with nicotine and glycerin collected on Cambridge filter pads. Experiments 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 (12)

1. An aerosol generating article for generating an inhalable aerosol upon heating, comprising:
A rod of an aerosol-generating substrate;
a mouthpiece segment comprising a plug of filtration material disposed downstream of and longitudinally aligned with said rod;
a hollow tubular segment at a location between the rod and the mouthpiece segment, the hollow tubular segment being longitudinally aligned with the rod and the mouthpiece segment, the hollow tubular segment defining a cavity extending all the way to the upstream end of the mouthpiece segment;
a ventilation zone at a location along the hollow tubular segment;
the rod of aerosol-generating substrate has a length of less than 35 millimeters;
an equivalent inside diameter of the hollow tubular segment at the location of the ventilation zone is at least 5.5 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, and the aerosol-generating article has an overall RTD of less than 70 millimeters _H2O (700 Pa). The aerosol generating article of claim 1, wherein the hollow tubular segment includes a wrapper, the wrapper surrounding the rod and the mouthpiece segment. The aerosol generating article of claim 1, wherein the hollow tubular segment comprises a tube formed from a cellulosic material. The aerosol-generating article of claim 3, wherein the heated aerosol-generating article further comprises a wrapper surrounding the rod, the tube, and the mouthpiece segment. The aerosol generating article according to any one of claims 1 to 3, wherein the equivalent inner diameter of the hollow tubular segment is substantially constant along the length of the hollow tubular segment. The aerosol-generating article of any one of claims 1 to 4, wherein the ventilation zone is located along the hollow tubular segment at least 2 millimeters from the upstream end of the mouthpiece segment. The aerosol-generating article according to any one of claims 1 to 6, wherein the aerosol-generating article has a breathability level of at least 10 percent. The aerosol-generating article according to any one of claims 1 to 7, wherein the aerosol-generating article has a breathability level of less than 60 percent. The aerosol-generating article according to any one of claims 1 to 8, wherein the hollow tubular segment has a length of 10 millimeters to 30 millimeters. The aerosol-generating article of any one of claims 1 to 9, wherein the peripheral wall thickness of the hollow tubular segment at the location of the ventilation zone is less than 1.5 millimeters. 11. An aerosol-generating article according to any one of claims 1 to 10, wherein the peripheral wall thickness of the hollow tubular segment at the location of the ventilation zone is at least 100 micrometers. An aerosol-generating article according to any one of claims 1 to 11, wherein the aerosol-generating article has an RTD of at least 30 millimetres H ₂ O (300 Pa).

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