CN113163850A

CN113163850A - Aerosol-generating article with ventilation cavity

Info

Publication number: CN113163850A
Application number: CN201980078041.3A
Authority: CN
Inventors: J·尤塞里
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2018-12-20
Filing date: 2019-12-20
Publication date: 2021-07-23
Also published as: BR112021009650A2; ZA202101962B; CA3116279A1; PH12021550666A1; IL283978B1; WO2020128043A1; AU2019410744A1; US20220007709A1; JP2022515329A; IL283978A; EP3897234A1; KR20210102283A; MX2021006881A

Abstract

An aerosol-generating article (10) for generating an inhalable aerosol upon heating comprising: a rod (12) of aerosol-generating substrate; a mouthpiece segment (18) comprising a filter segment of filter material and arranged downstream of and in longitudinal alignment with the rod (12); and a hollow tubular segment (16) between the rod (12) and the mouthpiece segment (18). The hollow tubular segment (16) is longitudinally aligned with the rod (12) and mouthpiece segment (18) and defines a cavity extending up to the upstream end of the mouthpiece segment (18). The article (10) further includes a vented zone (26) at a location along the hollow tubular section (16) that is less than 18 millimeters from the upstream end of the hollow tubular section (16). The peripheral wall of the hollow tubular section (16) has a thickness of less than about 1.5 mm. The rod (12) of aerosol-generating substrate comprises at least an aerosol former, the rod (12) having an aerosol former content of at least about 10% by dry weight. The aerosol generating article has a ventilation level of at least about 10%.

Description

Aerosol-generating article with ventilation cavity

Technical Field

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

Background

Aerosol-generating articles in which an aerosol-generating substrate (such as a tobacco-containing substrate) is heated rather than combusted are 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 positioned in contact with the heat source, either internally, around or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in air drawn through the aerosol-generating article. As the released compound cools, the compound condenses to form an aerosol.

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

In the past, randomly oriented fragments, strands or rods of tobacco material have typically been used to produce substrates for heated aerosol-generating articles. Alternatively, rods of heated aerosol-generating articles formed from gathered sheets of tobacco material have been proposed, for example in international patent application WO-A-2012/164009. The strips disclosed in WO-A-2012/164009 have A longitudinal porosity which allows air to be drawn through the strip. Effectively, the folds in the gathered sheet of tobacco material define longitudinal channels through the strip.

Alternative rods for heated aerosol-generating articles are known from international patent application WO-A-2011/101164. The rods formed from the strands of homogenized tobacco material 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 rod of WO-A-2011/101164 may also be formed from A strand 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 a heated aerosol-generating article typically also comprises an aerosol former, i.e. a compound or mixture of compounds which in use promotes aerosol formation and which is preferably substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-forming agents include: polyhydric alcohols such as propylene glycol, triethylene glycol, 1, 3-butylene glycol, and glycerin; esters of polyhydric alcohols, such as monoacetin, diacetin, or triacetin; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

It is also common to include one or more additional elements in the aerosol-generating article that are assembled in the same package as the substrate when heated to produce an inhalable aerosol. Examples of such additional elements include: a mouthpiece filter segment, a support element adapted to impart structural strength to the aerosol-generating article, a cooling element adapted to facilitate cooling of the aerosol prior to reaching the mouthpiece, and the like. However, although it has been proposed to include such additional elements in view of their beneficial effects, they generally complicate the overall structure of the aerosol-generating article and make its manufacture more complex and costly. Indeed, the manufacture of such multi-element aerosol-generating articles typically requires rather complex manufacturing machinery and combination machinery.

In view of this, aerosol-generating articles having a simpler structure have also been proposed. However, in the absence of certain additional components, such as an aerosol-cooling element, it may become more difficult to manufacture aerosol-generating articles that consistently provide satisfactory aerosol delivery and RTD to consumers.

Disclosure of Invention

Accordingly, it is desirable to provide an aerosol-generating article capable of providing consistent, satisfactory aerosol delivery to a consumer during use. Furthermore, it would be desirable to provide such an improved aerosol-generating article having a satisfactory RTD value. It is also desirable to provide such an aerosol-generating article that can be manufactured efficiently and at high speeds, preferably with low RTD variability from article to article. The present invention aims to provide a technical solution adapted to achieve at least one of the above mentioned desired results.

According to one aspect of the present invention there is provided an aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising: a rod of aerosol-generating substrate; a mouthpiece segment comprising a filter segment of filter material, the mouthpiece segment being arranged downstream of the rod and in longitudinal alignment 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 section defines a cavity extending all the way to the upstream end of the mouthpiece section. The aerosol-generating article further comprises a ventilation zone at a position along the hollow tubular section less than about 18 mm from the upstream end of the hollow tubular section. The wall thickness of the peripheral wall of the hollow tubular section is less than about 1.5 millimeters. The rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol former content of at least about 10% by dry weight.

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

When a user applies a flame to one end of a conventional cigarette and draws air through the other end, the cigarette is lit. The localized heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to be lit and the resulting combustion produces breathable smoke. In contrast, in heated aerosol-generating articles, an aerosol is generated by heating a flavour-generating substrate, such as tobacco. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles, as well as aerosol-generating articles in which an aerosol is generated by heat transfer from a combustible fuel element or heat source to a physically separate aerosol-forming material. For example, aerosol-generating articles according to the present invention find particular application in aerosol-generating systems comprising an electrically heated aerosol-generating device having an internal heater blade adapted for insertion into a rod of aerosol-generating substrate. Aerosol-generating articles of this type are described in the prior art (for example in european patent application EP 0822670).

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

In this specification, the term "tubular section" is used to denote an elongate element defining a lumen or airflow channel along its longitudinal axis. In particular, the term "tubular" will be used below with respect to a tubular element having a substantially cylindrical cross-section and defining at least one gas flow duct establishing 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 the major longitudinal axis of an aerosol-generating article, which direction extends between an upstream end and a downstream end 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 an aerosol-generating article with respect to the direction in which an aerosol is conveyed through the aerosol-generating article during use.

During use, air is drawn through the aerosol-generating article in the longitudinal direction. 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" denotes the dimension of a component of an aerosol-generating article in the longitudinal direction. For example, it may be used to indicate the dimension of the strip or elongate tubular member in the longitudinal direction.

The term "thickness of the peripheral wall of the tubular element" is used in the present description to denote the minimum distance, measured between the outer and inner surface of the wall, circumferentially defining the tubular element. In practice, the distance at a given position is measured in a direction locally substantially perpendicular to the outer and inner surfaces of the tubular element. For a tubular element having a substantially circular cross-section, the distance is measured in a substantially radial direction of the tubular element.

In some embodiments, the thickness of the peripheral wall of the tubular element is constant. In an alternative embodiment, 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 comprise a tapered section or the like. In embodiments where the thickness of the peripheral wall of the tubular element varies along the length of the tubular element, the "thickness of the peripheral wall of the tubular element" is considered to be an average calculated based on several values measured at minimum distances between the outer and inner surfaces of the wall at different positions along the length of the tubular element.

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

The expression "air-impermeable material" is used throughout the present specification to mean a material that does not allow fluids, in particular air and fumes, to pass through the voids or pores in the material. If the hollow tubular section is formed of a material that is impermeable to air and aerosol particles, the air and aerosol particles drawn through the hollow tubular section are forced to flow through an airflow duct defined by the interior of the hollow tubular section, but are unable to flow through the peripheral wall of the hollow tubular section.

As used in this specification, the term "homogenized tobacco material" encompasses any tobacco material formed by the 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 powdering one or both of tobacco lamina and tobacco stem. In addition, the homogenized tobacco material may include small amounts of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during processing, handling, and transport of the tobacco. The 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 air to pass through the material.

Throughout this specification, the term "ventilation level" is used to denote the volume ratio between the airflow entering the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the level of ventilation, the higher the dilution of the aerosol stream delivered to the consumer. The ventilation level is measured on the aerosol-generating article itself, i.e. without inserting the aerosol-generating article into a suitable aerosol-generating device adapted to heat the aerosol-generating substrate.

As briefly described above, the aerosol-generating article of the present invention comprises: a rod of aerosol-generating substrate; a mouthpiece segment comprising a filter segment of filter material; and a hollow tubular segment at a location between the rod and the mouthpiece segment. All three elements are longitudinally aligned. The rod of aerosol-generating substrate comprises at least one aerosol former.

The rod of aerosol-generating substrate has an aerosol former content of at least about 10% by dry weight compared to known aerosol-generating articles. Further, the hollow tubular section defines a cavity extending all the way to the upstream end of the mouthpiece section, and a ventilation zone is provided at a location along the hollow tubular section less than about 18 millimeters from the upstream end of the hollow tubular section. Additionally, the peripheral wall of the hollow tubular section has a thickness of less than about 1.5 millimeters.

By providing an aerosol-generating article in which a hollow tubular element is arranged between a rod of aerosol-generating substrate and a mouthpiece, wherein the hollow tubular element defines a cavity extending up to an upstream end of the mouthpiece segment, the overall structural complexity of the article may be significantly reduced compared to existing aerosol-generating articles. This advantageously simplifies the manufacturing process and reduces the complexity of the manufacturing and assembly equipment required to implement the manufacturing process.

One such aerosol-generating article does not comprise an aerosol-cooling element adapted to reduce the temperature of an 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 by the heating product and drawn through the hollow tubular element is achieved by providing a ventilation zone at a location along the hollow tubular section. Furthermore, the inventors have surprisingly found that by arranging the ventilation zone at a distance of less than 18 mm from the upstream end of the hollow tubular section, and by using a hollow tubular section having a peripheral wall with a thickness of less than 1.5 mm, the effect of increased aerosol dilution due to ventilation air entering the article can be counteracted.

Without wishing to be bound by theory, it is hypothesized that as the aerosol travels towards the mouthpiece segment, a sharp cooling of the aerosol stream is achieved due to the rapid reduction in temperature of the aerosol stream by the introduction of ventilation air which enters the aerosol stream at a location relatively close to the upstream end of the hollow tubular segment (i.e. sufficiently close to the heat source and the rod of aerosol-generating substrate), which has a beneficial effect on the coagulation and nucleation of aerosol particles. Thus, the overall ratio of aerosol particle phase to aerosol gas phase may be enhanced compared to existing non-ventilated aerosol-generating articles.

At the same time, keeping the thickness of the peripheral wall of the hollow tubular element below 1.5 mm ensures that the total internal volume of the hollow tubular element (which allows the aerosol to begin the nucleation process once the aerosol components have separated from the rod of aerosol-generating substrate) and that the cross-sectional surface area of the hollow tubular segment is effectively maximised, while ensuring that the hollow tubular segment has the necessary structural strength to prevent collapse of the aerosol-generating article and to provide some support for the rod of aerosol-generating substrate and that the RTD of the hollow tubular segment is minimised. A larger value of the cross-sectional surface area of the cavity of the hollow tubular section is understood to be associated with a reduced velocity of the aerosol flow travelling along the aerosol-generating article, which is also expected to favour aerosol nucleation. Furthermore, it appears that by using a hollow tubular section with a thickness below 1.5 mm, the diffusion of the ventilation air can be substantially prevented before it comes into contact and mixes with the aerosol flow, which is also understood to further favour the nucleation phenomenon. In practice, the effect of cooling on the formation of new aerosol particles can be enhanced by providing more controlled local cooling of the volatile material flow.

Indeed, the inventors have surprisingly found how the advantageous effects of enhanced nucleation can significantly counteract the less desirable dilution effects, such that satisfactory values of aerosol delivery are always achieved with aerosol-generating articles according to the present invention. This is particularly advantageous in "short" aerosol-generating articles, for example aerosol-generating articles in which the length of the rod of aerosol-generating substrate is less than about 40 millimetres, preferably less than 25 millimetres, even more preferably less than 20 millimetres, or in which the overall length of the aerosol-generating article is less than about 70 millimetres, preferably less than about 60 millimetres, even more preferably less than 50 millimetres. It will be appreciated that in such aerosol-generating articles there is little time and space for the aerosol to form and make the particulate phase of the aerosol available for delivery to the consumer.

Furthermore, since the hollow tubular element does not contribute substantially to the RTD of the aerosol-generating article, in aerosol-generating articles according to the invention, the overall RTD of the article may advantageously be fine-tuned by adjusting the length and density of the rod of aerosol-generating substrate or the length and density of the segment of filter material of the mouthpiece. This enables the manufacture of aerosol-generating substrates having a consistent and very accurate predetermined RTD such that satisfactory RTD levels can be provided to consumers even with ventilation.

Aerosol-generating articles according to the present invention can be manufactured in a continuous process which 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 outer diameter of the rod of aerosol-generating substrate is preferably approximately equal to the outer diameter of the aerosol-generating article.

Preferably, the rod of aerosol-generating substrate has an outer diameter of at least 5 millimetres. The rod of aerosol-generating substrate may have an outer diameter of between about 5mm and about 12 mm, for example between about 5mm and about 10mm or between about 6mm and about 8 mm. In a preferred embodiment, the rod of aerosol-generating substrate has an outer diameter within 7.2 mm to 10%.

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

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

In a preferred embodiment, the aerosol-generating substrate comprises one or more gathered sheets of homogenized tobacco material. Preferably, one or more sheets of homogenized tobacco material are textured. As used herein, the term "textured sheet" means a sheet that has been creased, embossed, gravure, perforated, or otherwise deformed. The textured sheet material used in the homogenized tobacco material of the present invention may include a plurality of spaced indentations, projections, perforations, or combinations thereof. According to a particularly preferred embodiment of the invention, the rod of aerosol-generating substrate comprises a gathered crimped sheet of homogenized tobacco material defined by a wrapper.

As used herein, the term "crimped sheet" is intended to be synonymous with the term "corrugated 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 substantially parallel to the cylindrical axis of the rod according to the invention. This advantageously facilitates the gathering of the crimped sheet of homogenised tobacco material to form the rod. It will be understood, however, that the crimped sheet of homogenized tobacco material for use in the present invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations disposed at acute or obtuse angles 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 invention may have a substantially uniform texture over substantially its entire surface. For example, a crimped sheet of homogenized tobacco material for making rods for use in aerosol-generating articles according to the invention may comprise a plurality of substantially parallel ridges or corrugations that are substantially evenly spaced across the width of the sheet.

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

The sheet or web of homogenized tobacco material for use in the aerosol-generating substrate may comprise one or more intrinsic binders (i.e. tobacco endogenous binders), one or more extrinsic binders (i.e. tobacco exogenous binders) or a combination thereof to aid in the agglomeration of particulate tobacco. Alternatively or additionally, the sheet of homogenized tobacco material for use in an aerosol-generating substrate may comprise other additives including, but not limited to, tobacco and non-tobacco fibres, aerosol-formers, humectants, plasticisers, flavourants, fillers, aqueous and non-aqueous solvents and combinations thereof.

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

Suitable non-tobacco fibres for inclusion in a sheet or web of homogenized tobacco material for use in an aerosol-generating substrate are known in the art and include, but are not limited to: cellulose fibers; softwood fibers; hardwood fibers; jute fibers and combinations thereof. Prior to inclusion in the sheet of homogenised tobacco material for use in an aerosol-generating substrate, the non-tobacco fibres may be treated by suitable procedures known in the art including, but not limited to: mechanical pulping, refining, chemical pulping, bleaching, kraft pulping, and combinations thereof.

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

Suitable aerosol-forming agents are known in the art and include, but are not limited to: polyhydric alcohols such as propylene glycol, triethylene glycol, 1, 3-butylene glycol, and glycerin; esters of polyhydric alcohols, such as glycerol mono-, di-or triacetate; and fatty acid esters of mono-, di-or polycarboxylic acids, such as dimethyldodecanedioate and dimethyltetradecanedioate.

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

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

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

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

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

The sheet or web of homogenized tobacco used in the aerosol-generating article of the invention may be manufactured by methods known in the art, for example the method disclosed in international patent application WO-A-2012/164009A 2. In a preferred embodiment, a sheet of homogenized tobacco material for use in an aerosol-generating article is formed from a slurry comprising particulate tobacco, guar gum, cellulose fibres and glycerine by a casting process.

Alternative arrangements of homogenized tobacco material for use in rods in aerosol-generating articles will be known to the skilled person and may comprise a plurality of stacked sheets of homogenized tobacco material, a plurality of elongate tubular elements formed from a wound strip of homogenized tobacco material about its longitudinal axis, or the like.

As a further alternative, the rod of aerosol-generating substrate may comprise a nicotine-containing material that is not tobacco-based, such as a sheet of a sorbent non-tobacco material loaded with nicotine (e.g. in the form of a nicotine salt) and an aerosol-former. Examples of such strips are described in the international application WO-A-2015/052652. Additionally or alternatively, the rod of aerosol-generating substrate may comprise non-tobacco plant material, for example 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 defined by a wrapper. The wrapper may be formed from a porous or non-porous sheet material. The wrapper may be formed from any suitable material or combination of materials. Preferably, the wrapper is a paper wrapper.

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

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

Preferably, the hollow tubular section is an annular tube bounding and defining an air gap within the aerosol-generating article. In effect, the hollow tubular section provides a chamber for volatile aerosol components released upon heating of the aerosol-generating substrate to accumulate and flow into. As briefly described above, this chamber extends longitudinally all the way to the upstream end of the mouthpiece. This means that there is no intermediate element provided between the hollow tubular segment and the mouthpiece, and 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 effectively reaches the upstream end of the mouthpiece. In more detail, aerosol flowing through the aerosol-generating article typically reaches the upstream end of the filter material segment of the mouthpiece.

Thus, in an aerosol-generating article according to the invention, the hollow tubular segment holds the rod of aerosol-generating substrate at a predetermined distance from the mouthpiece and an elongate airflow conduit is provided for aerosol formation and flow towards the mouthpiece. During use, a thermal gradient is established along this gas flow duct. In effect, a temperature differential is provided such that the temperature of the volatile aerosol components entering the hollow tubular segment at the upstream end is greater than the temperature of the volatile aerosol components exiting the hollow tubular segment at the downstream end (i.e. the upstream end of the mouthpiece).

In one aspect, the hollow tubular section needs to withstand any axial compressive load or bending moment that may be applied to the hollow tubular section during manufacture of the aerosol-generating article. Furthermore, the hollow tubular section needs to impart structural strength to the aerosol-generating article so that it can be easily handled by a consumer and inserted into an aerosol-generating device for use. On the other hand, it is desirable that the total volume of the cavity defined by the interior of the hollow tubular element is as large as possible in order to facilitate aerosol formation and enhance aerosol delivery to the consumer.

To meet these requirements, the peripheral wall of the hollow tubular section has a thickness of less than 1.5 mm, as briefly described above. Preferably, the thickness of the peripheral wall of the hollow tubular section is less than 1250 microns, more preferably less than 1000 microns, even more preferably less than 900 microns. In a particularly preferred embodiment, the peripheral wall of the hollow tubular section has a thickness of less than 800 microns.

Additionally or alternatively, the peripheral wall of the hollow tubular section has a thickness of at least about 100 microns. Preferably, the peripheral wall of the hollow tubular section has a thickness of at least about 200 microns.

Preferably, the equivalent internal diameter of the hollow tubular section is at least about 4 mm. The term "equivalent internal diameter" is used herein to mean the diameter of a circle having the same surface area as the cross-section of the gas flow conduit defined by the interior of the hollow tubular section. The cross-section of the gas flow conduit may have any suitable shape. However, as briefly described above, a circular cross-section is preferred, i.e. the hollow tubular section is in fact a cylindrical tube. In this case, the equivalent internal diameter of the hollow tubular section effectively coincides with the internal diameter of the cylindrical tube.

In a preferred embodiment, the equivalent internal diameter of the hollow tubular section is at least about 5mm, more preferably at least about 5.25 mm, even more preferably at least about 5.5 mm. In some embodiments, the equivalent inner diameter of the hollow tubular section is at least about 6 millimeters or at least about 6.5 millimeters or at least about 7 millimeters.

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

The equivalent internal diameter of the hollow tubular section is measured at the location of the ventilation zone.

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

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

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

The total length of the aerosol-generating article according to the invention is preferably at least about 40 mm. Additionally or alternatively, the aerosol-generating article according to the present invention preferably has an overall length of less than about 70 mm, more preferably less than 60 mm, even more preferably less than 50 mm. In a preferred embodiment, the total length of the aerosol-generating article is from about 40 mm to about 70 mm. In some exemplary embodiments, the total length of the aerosol-generating article is about 45 millimeters.

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

In some embodiments, the hollow tubular section comprises a wrapper that also defines the rod and the mouthpiece section. Indeed, wrappers having a thickness falling within the above ranges are used to define and connect the rod and mouthpiece segment of aerosol-generating substrate, the wrappers effectively forming the peripheral wall of the hollow tubular element.

For example, one such combined wrapper of the connector strip and the mouthpiece segment may have a basis weight of less than at least about 70 grams per square meter (gsm). Preferably, one such combination wrapper of the connecting rod and the mouthpiece segment has a basis weight of at least about 80 grams per square meter, more preferably at least about 90 grams per square meter. In a particularly preferred embodiment, the combined wrapper of the connecting strip and the mouthpiece section has a basis weight of at least about 110 grams per square meter, 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 defining the rod, the tube and the mouthpiece segment. For example, the cellulosic material may comprise paper or paperboard or mixtures thereof.

For example, the hollow tubular section may comprise a tube formed from an extruded plastic tube. Alternatively, the hollow tubular section may comprise a tube formed from a plurality of overlapping paper layers, such as a plurality of parallel wound paper layers or a plurality of helically wound paper layers. Forming the tube from a plurality of overlapping paper layers may help to further improve collapse or deformation resistance. Preferably, the tube comprises two or more paper layers. Alternatively or additionally, the tube preferably comprises less than eleven paper layers.

One such tube may be made impermeable to air by using a paper that is substantially impermeable to air. The term "substantially air impermeable paper" is used herein to denote a paper having an air permeability of less than about 20 CORESTA units, more preferably less than about 10 CORESTA units, most preferably less than about 5 CORESTA units, as measured according to ISO 2965: 2009. Alternatively, adjacent paper layers in the tube may be held together with an adhesive to impart sealing properties to the tube.

Suitable materials for forming the tube are known in the art and include, but are not limited to, cellulose acetate, hard paper (i.e., paper having a basis weight of at least 90 grams per square meter), polymeric films such as cellulose film and paperboard.

In some embodiments, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is preferably less than 1 mg/cubic millimeter. In a particularly preferred embodiment, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is less than 0.5. More preferably, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is less than 0.2 mg/cubic millimeter. Even more preferably, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is less than 0.1 mg/cubic millimeter.

In a hollow tubular segment in which the ratio between the weight of the hollow tubular segment and the volume of the lumen defined by the hollow tubular segment falls within the above ranges, the volume of the lumen is advantageously maximised whilst ensuring that the hollow tubular segment contributes to the overall structural strength of the aerosol-generating article and effectively maintains the rod of aerosol-generating substrate spaced from the mouthpiece.

In an exemplary embodiment, the hollow tubular section has an internal equivalent diameter of 7 millimeters and is formed from a wrapper having a basis weight of 110gsm and a weight of 2.5 milligrams/millimeter. For one such hollow tubular section, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is about 0.065 mg/cubic millimeter.

In another exemplary embodiment, the hollow tubular section has an internal equivalent diameter of 5.3 millimeters and may be provided as a cellulose acetate tube weighing 9.5 milligrams/millimeter. For one such hollow tubular section, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section is about 0.43 mg/cubic millimeter.

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

Additionally or alternatively, the distance between the vented zone and the upstream end of the hollow tubular section is preferably at least 2 mm. More preferably, the distance between the vented zone and the upstream end of the hollow tubular section is at least about 4 millimeters. Even more preferably, the distance between the vented zone and the upstream end of the hollow tubular section is at least about 6 millimeters.

The ventilation zone may be disposed at a location along the hollow tubular segment at least 2mm from the upstream end of the mouthpiece. Preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 4mm from the upstream end of the mouthpiece. Preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 5mm 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 6mm from the upstream end of the mouthpiece.

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

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

When the mixture of air and aerosol particles flowing through the aerosol-generating article reaches the ventilation zone, external air drawn into the hollow tubular section 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, as will be discussed in more detail below, by providing the ventilation zone at a distance from the upstream end of the mouthpiece segment falling within the above ranges, the cooling chamber is effectively disposed immediately upstream of the mouthpiece, wherein nucleation and growth of aerosol particles is advantageously promoted. Thus, the dilution effect of the ventilation air into the hollow tubular section is at least partially counteracted, which advantageously enables to provide a consumer-satisfactory aerosol delivery level.

Preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 10mm 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 mm 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 mm from the downstream end of the mouthpiece segment. This is advantageous as it ensures that the vented zone is not obscured by the lips of the consumer during use.

Additionally or alternatively, the ventilation zone is preferably at a location along the hollow tubular segment less than 25 mm from the downstream end of the mouthpiece segment. More preferably, the ventilation zone is at a location along the hollow tubular section less than 20 mm from the downstream end of the mouthpiece section. This advantageously ensures that, during use, when the aerosol-generating article is received within the heating chamber of an electrically heated aerosol-generating device, the ventilation zone is effectively at a location along the hollow tubular section that projects outside the heating chamber so that external cooling air can be easily drawn into the hollow tubular section.

In some preferred embodiments, the ventilation zone is provided along the hollow tubular segment at a location from about 10mm to about 25 mm from the downstream end of the mouthpiece segment, more preferably from about 12 mm to about 20 mm from the downstream end of the mouthpiece segment. In an exemplary embodiment, the ventilation zone is disposed at a location along the hollow tubular segment that is 18 millimeters from the downstream end of the mouthpiece segment. In another exemplary embodiment, the ventilation zone is provided at a location along the hollow tubular segment 13 mm from the downstream end of the mouthpiece segment.

Aerosol-generating articles may generally have a ventilation level of at least about 10%, preferably at least about 20%.

In preferred embodiments, the aerosol-generating article has a ventilation level of at least about 20% or 25% or 30%. More preferably, the aerosol-generating article has a ventilation level of at least about 35%. Additionally or alternatively, the aerosol-generating article preferably has a ventilation level of less than about 60%. More preferably, the aerosol-generating article has a ventilation level of less than about 50% or less than about 40%. In particularly preferred embodiments, the aerosol-generating article has a ventilation level of from about 25% to about 60%. More preferably, the aerosol generating article has a ventilation level of from about 28% to about 42%. In some particularly preferred embodiments, the aerosol-generating article has a ventilation level of about 35%.

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

The formation of aerosols from gaseous mixtures containing various chemicals depends on subtle interactions between nucleation, evaporation and condensation and coalescence, while also taking into account changes in vapor concentration, temperature and velocity fields. The classical nucleation theory is based on the following assumptions: a portion of the molecules in the gas phase are large enough to remain adhered for a sufficient period of time with a sufficient probability (e.g., half the probability). These molecules represent some critical threshold molecular cluster in transient molecular aggregates, which means that, in general, smaller molecular clusters are likely to break down into the gas phase rather quickly, while larger clusters are likely to grow. Such critical clusters are considered to be key nucleation cores from which droplets are expected to grow due to molecular condensation from the vapor. The just nucleated initial droplet is assumed to appear at some original diameter and can then grow several orders of magnitude. This is facilitated and may be enhanced by rapid cooling of the surrounding steam to cause condensation. In this regard, it should be kept in mind that evaporation and condensation are two aspects of the same mechanism, namely gas-liquid mass transfer. While evaporation involves a net mass transfer from the liquid droplet to the gas phase, condensation is a net mass transfer from the gas phase to the liquid droplet phase. Evaporation (or condensation) will shrink (or grow) the droplets but will not change the number of droplets.

In such a situation, which may be further complicated by coalescence phenomena, the temperature and rate of cooling may play a key role in determining how the system responds. In general, different cooling rates may lead to significantly different temporal behavior with respect to liquid phase (droplet) formation, since the nucleation process is typically non-linear. Without wishing to be bound by theory, it is hypothesized that cooling may cause a rapid increase in the number concentration of droplets, which is followed by a strong transient increase in this growth (nucleation burst). At lower temperatures, this nucleation burst appears to be more pronounced. Furthermore, it appears that a higher cooling rate may favor an earlier onset of nucleation. In contrast, a decrease in the cooling rate appears to have a beneficial effect on the final size that the aerosol droplets eventually reach.

Thus, the rapid cooling induced by the external air entering the hollow tubular section via the ventilation zone may advantageously be used to promote nucleation and growth of aerosol droplets. At the same time, however, having the outside air enter the hollow tubular section has the direct disadvantage 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 by measuring the delivery effect of glycerol as aerosol former, in particular included in the aerosol-generating substrate) is advantageously minimized when the ventilation level is between 30% and 50%. In particular, it has been found that ventilation levels between 35% and 42% result in particularly satisfactory glycerol delivery values. At the same time, the degree of nucleation and hence the delivery of nicotine and aerosol former (e.g. glycerol) is improved.

In addition, the present inventors have found that in aerosol-generating articles according to the present invention, the cooling and dilution effect caused by the entry of ventilation air at a location along the duct defined by the hollow tubular section described above has an unexpected reducing effect on the generation and delivery of phenol-containing substances.

The plenum may comprise one or more rows of perforations formed through the peripheral wall of the hollow tubular section. Preferably, the ventilation zone comprises only one row of perforations. This is understood to be advantageous in that aerosol nucleation may be further enhanced by concentrating the cooling effect produced by ventilation over a short portion of the cavity defined by the hollow tubular section. This is because a faster and more intense cooling of the volatile material is expected to be particularly advantageous for the formation of new nuclei of aerosol particles.

Preferably, one or more rows of perforations are arranged circumferentially around the wall of the hollow tube. Where the plenum comprises two or more rows of perforations formed through the peripheral wall of the hollow tubular section, the rows are longitudinally spaced from one another along the hollow tubular section. For example, adjacent rows of perforations may be longitudinally spaced from each other by a distance of between about 0.25 millimeters and 0.75 millimeters.

The equivalent diameter of at least one of the vent perforations is preferably at least about 100 microns. Preferably, the equivalent diameter of at least one of the vent perforations is at least about 150 microns. Even more preferably, the equivalent diameter of at least one of the vent perforations is at least about 200 microns. Additionally or alternatively, the equivalent diameter of at least one of the ventilation perforations is preferably less than about 500 microns. More preferably, the equivalent diameter of at least one of the vent perforations is less than about 450 microns. Even more preferably, the equivalent diameter of at least one of the vent perforations is less than about 400 microns. 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 ventilation perforations. The cross-section of the ventilation perforations may have any suitable shape. However, circular ventilation perforations are preferred.

The ventilation perforations may be of uniform size. Alternatively, the size of the ventilation perforations may vary. By varying the number and size of the ventilation perforations, the amount of outside air entering the hollow tubular segment can be adjusted during use when a consumer draws on the mouthpiece of the aerosol-generating article. Thus, the ventilation level of the aerosol-generating article may advantageously be adjusted.

The ventilation perforations may be formed using any suitable technique (e.g. by laser techniques) by mechanically perforating a hollow tubular section that is part of the aerosol-generating article or by pre-perforating a hollow tubular section before it is combined with other elements to form the aerosol-generating article. Preferably, the vent perforations are formed by in-line laser perforation.

In the aerosol-generating article according to the invention, the total RTD of the article is substantially dependent on the RTD of the rod and the RTD of the mouthpiece, since the hollow tubular section is substantially empty and therefore substantially contributes only slightly to the total RTD. In practice, the hollow tubular section may be adapted to produce a range of about 0mm H₂O (about 0Pa) to about 20 mm H₂RTD of O (about 200 Pa). Preferably, inThe hollow tubular section is adapted to produce about 0mm H₂O (about 0Pa) and about 10mm H₂RTD between O (about 100 Pa).

The aerosol-generating article preferably has an H of less than about 90 mm₂Total RTD of O (about 900 Pa). More preferably, the aerosol-generating article has a H of less than about 80 mm₂Total RTD of O (about 800 Pa). Even more preferably, the aerosol-generating article has a H of less than about 70 mm₂Total RTD of O (about 700 Pa).

Additionally or alternatively, the aerosol-generating article preferably has a H of at least about 30 mm₂Total RTD of O (about 300 Pa). More preferably, the aerosol-generating article has a H of at least about 40 mm₂Total RTD of O (about 400 Pa). Even more preferably, the aerosol-generating article has a H of at least about 50 mm₂Total RTD of O (about 500 Pa).

The RTD of the aerosol-generating article may be assessed as the negative pressure that must be applied to the downstream end of the mouthpiece under the test conditions defined in ISO 3402 in order to maintain a steady volumetric flow of 17.5ml/s of air through the mouthpiece. The RTD values listed above are intended to be measured on the aerosol-generating article alone (i.e. prior to insertion of the article into the aerosol-generating device) without blocking the perforations of the ventilation zone.

The length and density (denier per filament count) of the filter material of the mouthpiece may be adjusted if desired or needed, 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. For example, such additional filter sections may be comprised between a rod of aerosol-generating substrate and a hollow tubular section. Preferably, such additional filter segments comprise a filtration material, such as cellulose acetate. Preferably, the length of the additional filter section is between about 4mm and about 8mm, more preferably between about 5mm and about 7 mm.

In some embodiments, aerosol-generating articles according to the present invention may comprise an additional support element arranged between and in longitudinal alignment with the rod and the hollow tubular section of the aerosol-generating substrate. In more detail, the support element is preferably arranged immediately downstream of the strip 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, and polymeric materials, such as Low Density Polyethylene (LDPE). In a preferred embodiment, the support element is provided as a hollow cellulose acetate tube.

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

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

The support element may be between about 5 millimeters and about 15 millimeters in length. In a preferred embodiment, the support element has a length of about 8 mm.

During insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article, some force may need to be applied by the user in order to overcome the resistance of the aerosol-forming substrate of the aerosol-generating article to the insertion of the heating element of the aerosol-generating device. This may damage one or both of the aerosol-generating article and the heating element of the aerosol-generating device. 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 incomplete insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate, which may result in uneven and inefficient heating of the aerosol-forming substrate of the aerosol-generating article. The support element is advantageously configured to resist downstream movement of the aerosol-forming substrate during insertion of the heating element of the aerosol-generating device into the aerosol-forming substrate of the aerosol-generating article.

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

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

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

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

In effect, the plenum divides the cavity defined by the interior of the hollow tubular section into an upstream sub-cavity extending longitudinally from the upstream end of the hollow tubular section to the location of the plenum and a downstream sub-cavity extending longitudinally from the location of the plenum to the downstream end of the hollow tubular section. Without wishing to be bound by theory, it will be appreciated that in the upstream sub-cavity, by generating some heat to the peripheral wall of the hollow tubular segment, the volatile material of the aerosol stream advancing along the hollow tubular segment slowly cools and thus the aerosol particles start to nucleate. On the other hand, in the downstream sub-chamber, the aerosol flow and the ventilation air are rapidly mixed, which causes a rapid cooling of the volatile substances of the aerosol flow and thus favours the nucleation of new aerosol particles and promotes the growth of existing aerosol particles as the aerosol advances towards the mouthpiece.

Preferably, the ratio between the length of the upstream chamber and the length of the downstream chamber is less than 5 or less than 3 or less than 1.5. More preferably, the ratio between the length of the upstream chamber and the length of the downstream chamber is less than 1.2 or less than 1. Even more preferably, the ratio between the length of the upstream chamber and the length of the downstream chamber is less than 0.67.

Additionally or alternatively, the ratio between the length of the upstream chamber and the length of the downstream chamber is preferably at least about 0.15. More preferably, the ratio between the length of the upstream chamber and the length of the downstream chamber is preferably at least about 0.2. Even more preferably, the ratio between the length of the upstream chamber and the length of the downstream chamber is preferably at least about 0.35.

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

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

Additionally or alternatively, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is preferably at least about 0.25. More preferably, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is at least about 0.33. Even more preferably, the ratio between the length of the upstream section of the aerosol-generating article and the length of the downstream section of the aerosol-generating article is at least about 0.5.

In aerosol-generating articles according to the invention, it is advantageously easy 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 limited small number of components, and the provision of the ventilation zone also helps to reduce the overall RTD of the article. Thus, it may be advantageous to reduce RTD variability between aerosol-generating articles.

Accordingly, the present invention may also provide a package 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 of the at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD of the at least ten aerosol-generating articles is less than 10mm H₂O (about 100 pascals). Preferably, in one such package, the difference between the RTD of the aerosol-generating article having the highest RTD of the at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD of the at least ten aerosol-generating articles is less than 9mm H₂O (about 90 pascals), more preferably less than 8mm H₂O (about 80 pascals), even more preferably less than 7mm H₂O (about 70 pascal) or 6mm H₂O (about 60 pascals) or 5mm H₂O (about 50 pascal) or 4mm H₂O (about 40 pascals) or 3mm H₂O (about 30 pascals) or 2mm H₂O (about 20 pascals).

Drawings

The invention will be further described hereinafter with reference to the drawings of the accompanying drawings, in which:

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

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

figure 3 shows a schematic side cross-sectional view of a further embodiment of an aerosol-generating article according to the invention.

Detailed Description

The aerosol-generating article 10 shown in figure 1 comprises a rod 12 of aerosol-generating substrate, a hollow cellulose acetate tube 14, a hollow tubular segment 16 and a mouthpiece segment 18. These four elements are arranged in end-to-end longitudinal alignment and are defined by the 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 located at the end of the article opposite the mouth end 22. The aerosol-generating article 10 shown in figure 1 is particularly suitable for use with an electrically operated aerosol-generating device comprising a heater for heating a rod of aerosol-generating substrate.

The rod 12 of aerosol-generating substrate is about 12 mm in length and about 7mm in diameter. The strip 12 is cylindrical and has a substantially circular cross-section. The rod 12 comprises an aggregated sheet of homogenized tobacco material. The sheet of homogenized tobacco material comprises 10% glycerol on a dry basis. The hollow cellulose acetate tube 14 has a length of about 8 millimeters and a thickness of 1 millimeter.

The tobacco plug segment 18 comprises a filter segment of 8 denier per filament cellulose acetate tow and has a length of about 7 millimeters.

The hollow tubular section 14 is provided as a cylindrical tube having a length of about 18 millimeters and the thickness of the tube wall is about 100 micrometers.

In more detail, the hollow tubular section 16 may be formed, for example, from paper having a basis weight of 110gsm and having a weight of 45 milligrams (i.e., 2.5 milligrams per millimeter of length). The equivalent internal diameter of the hollow tubular section 16 is about 7 mm. Thus, the volume of the cavity defined by the interior of the hollow tubular section 16 is about 693 cubic millimeters. Thus, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section 16 is about 0.065.

The aerosol-generating article 10 comprises a ventilation zone 26 disposed about 5mm from the upstream end of the mouthpiece segment 18. Thus, the ventilation zone 26 is about 12 mm from the downstream end of the aerosol-generating article and about 13 mm from the upstream end of the hollow tubular section. Thus, the venting zone 26 is about 21 mm from the downstream end of the strip 12.

Figure 2 shows another example of an aerosol-generating article according to the present invention. The aerosol-generating article 30 of fig. 2 has the same structure as the aerosol-generating article 10 of fig. 1, and differs significantly from the aerosol-generating article 10 only over the length of certain components, and is described below only insofar as it differs from the aerosol-generating article 10. In the following, identical reference numerals will be used, where possible, for corresponding parts having identical structure or function.

In the aerosol-generating article 30 of fig. 2, the rod 12 and the hollow cellulose acetate tube 14 have the same length as in the aerosol-generating article 10 of fig. 1. However, the mouthpiece segment comprises a filter segment of cellulose acetate tow of 11 denier per filament and having a length of about 12 mm, and a hollow tubular segment 14 of about 13 mm in length. The ventilation zone 26 is located about 6mm from the upstream end of the mouthpiece segment 18 and about 7mm from the upstream end of the hollow tubular segment. Thus, the ventilation zone 26 is about 15 mm from the downstream end of the strip 12.

In the embodiment of fig. 2, the hollow tubular section 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 per millimeter of length).

The equivalent inner diameter of the hollow tubular section 16 may be about 5.3 millimeters. Thus, the volume of the cavity defined by the interior of the hollow tubular section 16 is about 397 cubic millimeters. Thus, the ratio between the weight of the hollow tubular section and the volume of the lumen defined by the hollow tubular section 16 is about 0.43.

Figure 3 shows a further example of an aerosol-generating article according to the present invention. The aerosol-generating article 40 of figure 3 differs in construction from the aerosol-generating device 10 of figure 1 and the aerosol-generating article 30 of figure 2 in that it does not comprise a hollow cellulose acetate tube as a support element. Accordingly, the three main components also differ in length. In the following, identical reference numerals will be used, where possible, for corresponding parts having identical structure or function.

In the aerosol-generating article 40 of figure 3, the rod 12 has a length of about 12 millimetres, the hollow tubular section 14 has a length of about 26 millimetres, and the mouthpiece section 18 comprises a filter section of cellulose acetate tow having a length of about 12 millimetres and a denier per filament of 11. The ventilation zone 26 is located about 5mm from the upstream end of the mouthpiece segment 18 and about 21 mm from the upstream end of the hollow tubular segment, which in this embodiment coincides with the downstream end of the rod 12.

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

Example 1 this experiment was conducted to evaluate the effect of incorporating a hollow tubular section with a venting zone provided at a location along the hollow tubular section in accordance with the present invention. The effect of ventilation levels on the delivery of nicotine and aerosol former (glycerol) was investigated. Comparative measurements with a reference aerosol-generating article without ventilation are also provided.

Materials and methods

Article a is an aerosol-generating article formed from: a rod of aerosol-generating substrate comprising a gathered sheet of homogenized tobacco material and about 18% glycerin by dry weight, said rod having a length of 12 mm; a support element in the form of a hollow cellulose acetate tube aligned with and immediately downstream of the strip, the support element having a length of 8 mm; a hollow tubular section in the form of a cardboard tube, aligned with and immediately downstream of the strip, the hollow tubular section having a length of 13 mm; a mouth segment of filter material aligned with and immediately downstream of the hollow tubular segment, the mouth segment having a length of 12 millimeters. The ventilation zone was located 18 mm from the downstream end of the mouthpiece section along the hollow tubular section. The level of ventilation of the aerosol-generating article a was 30%.

Article B is a reference aerosol-generating article having the same structure as article a but no ventilation zone. Thus, the ventilation level of the aerosol-generating article B is 0%.

Nicotine and glycerol delivery amounts were measured by gas chromatography/time of flight mass spectrometry (GC/MS-TOF) on nicotine and glycerol collected on cambridge filter pads. The experiment was performed as described in example 1.

And (6) obtaining the result. The average nicotine and glycerol delivery for product a and product B is shown in table 1 below.

TABLE 1 Effect of ventilation levels on nicotine and glycerol delivery.

Claims

1. An aerosol-generating article for generating an inhalable aerosol upon heating, the aerosol-generating article comprising:

a rod of aerosol-generating substrate;

a mouthpiece segment comprising a filter segment of filter material, the mouthpiece segment being arranged downstream of and in longitudinal alignment with the rod; and

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, wherein the hollow tubular segment defines a cavity extending up to an upstream end of the mouthpiece segment;

a ventilation zone at a location along the hollow tubular section less than about 18 millimeters from an upstream end of the hollow tubular section;

wherein the peripheral wall of the hollow tubular section has a thickness of less than about 1.5 millimeters;

wherein the rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol former content of at least about 10% by dry weight; and is

Wherein the aerosol generating article has a ventilation level of at least about 10%.

2. An aerosol-generating article according to claim 1, wherein the hollow tubular section comprises a wrapper, the wrapper further defining the rod and the mouthpiece section.

3. An aerosol-generating article according to claim 1, in which the hollow tubular section comprises a tube formed from a polymeric or cellulosic material, the heated aerosol-generating article further comprising a wrapper defining the rod, the tube and the mouthpiece section.

4. An aerosol-generating article according to any preceding claim, wherein the ventilation zone is at a position along the hollow tubular section at least 2mm from the upstream end of the mouthpiece section.

5. An aerosol-generating article according to claim 4, wherein the ventilation zone is at a position along the hollow tubular section less than 25 mm from a downstream end of the mouthpiece section.

6. An aerosol-generating article according to any preceding claim, wherein the aerosol-generating article has a ventilation level of less than about 60%.

7. An aerosol-generating article according to any preceding claim, wherein the rod has a length of less than about 15 millimetres.

8. An aerosol-generating article according to any preceding claim, wherein the hollow tubular section has a length of between about 10 millimetres and about 30 millimetres.

9. An aerosol-generating article according to any preceding claim, wherein the total length of the aerosol-generating article is from about 40 mm to about 70 mm.

10. An aerosol-generating article according to any preceding claim, wherein the hollow tubular segment has a thickness of at least about 100 microns.

11. An aerosol-generating article according to any preceding claim, wherein the inner equivalent diameter of the hollow tubular section at the location of the ventilation zone is at least about 4 millimetres.

12. An aerosol-generating article according to any preceding claim, wherein the RTD of the aerosol-generating article is at about 30 mm H₂O and about 90 mm H₂And O is between.

13. An aerosol-generating article according to any preceding claim, wherein the ventilation zone comprises a single row of apertures formed through the peripheral wall of the hollow tubular section.

14. A package comprising at least ten aerosol-generating articles according to any preceding claim, wherein the difference between the RTD of the aerosol-generating article having the highest RTD of the at least ten aerosol-generating articles and the RTD of the aerosol-generating article having the lowest RTD of the at least ten aerosol-generating articles is less than 10mm H₂O。