Classifications

• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24C—MACHINES FOR MAKING CIGARS OR CIGARETTES
  • A24C5/00—Making cigarettes; Making tipping materials for, or attaching filters or mouthpieces to, cigars or cigarettes
  • A24C5/14—Machines of the continuous-rod type
  • A24C5/18—Forming the rod
  • A24C5/1885—Forming the rod for cigarettes with an axial air duct
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24C—MACHINES FOR MAKING CIGARS OR CIGARETTES
  • A24C5/00—Making cigarettes; Making tipping materials for, or attaching filters or mouthpieces to, cigars or cigarettes
  • A24C5/14—Machines of the continuous-rod type
  • A24C5/18—Forming the rod
  • A24C5/1892—Forming the rod with additives, e.g. binding agent, flavorants
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D1/00—Cigars; Cigarettes
  • A24D1/002—Cigars; Cigarettes with additives, e.g. for flavouring
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D1/00—Cigars; Cigarettes
  • A24D1/02—Cigars; Cigarettes with special covers
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D1/00—Cigars; Cigarettes
  • A24D1/02—Cigars; Cigarettes with special covers
  • A24D1/027—Cigars; Cigarettes with special covers with ventilating means, e.g. perforations
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D1/00—Cigars; Cigarettes
  • A24D1/04—Cigars; Cigarettes with mouthpieces or filter-tips
  • A24D1/042—Cigars; Cigarettes with mouthpieces or filter-tips with mouthpieces
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D1/00—Cigars; Cigarettes
  • A24D1/20—Cigarettes specially adapted for simulated smoking devices
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D3/00—Tobacco smoke filters, e.g. filter-tips, filtering inserts; Filters specially adapted for simulated smoking devices; Mouthpieces for cigars or cigarettes
  • A24D3/02—Manufacture of tobacco smoke filters
  • A24D3/0275—Manufacture of tobacco smoke filters for filters with special features
  • A24D3/0279—Manufacture of tobacco smoke filters for filters with special features with tubes
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D3/00—Tobacco smoke filters, e.g. filter-tips, filtering inserts; Filters specially adapted for simulated smoking devices; Mouthpieces for cigars or cigarettes
  • A24D3/04—Tobacco smoke filters characterised by their shape or structure
  • A24D3/043—Tobacco smoke filters characterised by their shape or structure with ventilation means, e.g. air dilution
• • A—HUMAN NECESSITIES
  • A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
  • A24D—CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES FOR CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
  • A24D3/00—Tobacco smoke filters, e.g. filter-tips, filtering inserts; Filters specially adapted for simulated smoking devices; Mouthpieces for cigars or cigarettes
  • A24D3/04—Tobacco smoke filters characterised by their shape or structure
  • A24D3/048—Tobacco smoke filters characterised by their shape or structure containing additives

Definitions

• the present invention relates to an aerosol generating article comprising an aerosol-generating substrate and adapted to produce 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 known in the art.
• an aerosol is generated by the transfer of 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.
• 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.
• 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 the transfer of heat from one or more electrical heater elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article.
• Substrates for heated aerosol-generating articles have, in the past, typically been produced using randomly oriented shreds, strands, or strips of tobacco material.
• rods for heated aerosol-generating articles have been proposed, for example in international patent application WO-A-2012/164009 , that are formed from gathered sheets of tobacco material.
• the rods disclosed in WO-A-2012/164009 have a longitudinal porosity that allows air to be drawn through the rods. Effectively, folds in the gathered sheets of tobacco material define longitudinal channels through the rod.
• Substrates for heated aerosol-generating articles typically further comprise an aerosol former, that is, a compound or mixture of compounds that, in use, facilitates formation of the aerosol and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article.
• aerosol-formers include: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerin; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.
• an aerosol-generating article for producing an inhalable aerosol upon heating one or more additional elements that are assembled with the substrate in a same wrapper.
• additional elements include a mouthpiece filtration segment, a support element adapted to impart structural strength to the aerosol-generating article, a cooling element adapted to favour cooling of the aerosol prior to reaching the mouthpiece, and so forth.
• additional elements include a mouthpiece filtration segment, a support element adapted to impart structural strength to the aerosol-generating article, a cooling element adapted to favour cooling of the aerosol prior to reaching the mouthpiece, and so forth.
• aerosol-generating articles have also been proposed that have a simpler structure.
• additional components such as, for example, an-aerosol-cooling element, it may become more difficult to manufacture aerosol-generating articles that consistently provide the consumer with a satisfactory aerosol delivery and RTD.
• WO 2017/198838 A1 discloses an aerosol-generating article 101 adapted for use with an apparatus having a power source and a heater.
• the article 101 of one example is in the form of a substantially cylindrical rod that includes a body of smokable material 103 and a filter assembly 105 in the form of a rod.
• the filter assembly 105 includes three segments, a cooling segment 107, a filter segment 109 and a mouth end segment 111.
• the body of smokable material 103 is located towards the distal end 115 of the article 101.
• the cooling segment 107 is located adjacent the body of smokable material 103 between the body of smokable material 103 and the filter segment 109, such that the cooling segment 107 is in an abutting relationship with the smokable material 103 and the filter segment 103.
• the filter segment 109 is located in between the cooling segment 107 and the mouth end segment 111.
• the mouth end segment 111 is located towards the proximal end 113 of the article 101, adjacent the filter segment 109.
• the smokable material may include an aerosol forming agent, such as glycerol.
• the total length of the article 101 is between 71 mm and 95mm, more preferably, total length of the article 101 is between 79mm and 87mm, more preferably still, total length of the article 101 is 83mm.
• the cooling segment 107 is an annular tube and is located around and defines an air gap within the cooling segment. In one example the length of the cooling segment 107 is at least 15mm. In one example, the length of the cooling segment 107 is between 20mm and 30mm, more particularly 23mm to 27mm, more particularly 25mm to 27mm and more particularly 25mm.
• a ventilation region 317 is provided in the article 301 to enable air to flow into the interior of the article 301 from the exterior of the article 301.
• the ventilation region 317 takes the form of one or more ventilation holes 317 formed through the outer layer of the article 301.
• the ventilation holes may be located in the cooling segment 307 to aid with the cooling of the article 301.
• the ventilation region 317 comprises one or more rows of holes, and preferably, each row of holes is arranged circumferentially around the article 301 in a cross-section that is substantially perpendicular to a longitudinal axis of the article 301.
• the rows of ventilation holes 317 are located at least 11mm from the proximal end 313 of the article, more preferably the ventilation holes are located between 17mm and 20mm from the proximal end 313 of the article 301.
• the location of the ventilation holes 317 is positioned such that user does not block the ventilation holes 317 when the article 301 is in use.
• an aerosol generating article that enables the provision of a consistently satisfactory aerosol delivery to the consumer during use. Further, it would be desirable to provide one such improved aerosol-generating article that has a satisfactory RTD value. It would be equally desirable to provide one such aerosol-generating article that can be manufactured efficiently and at high speed, preferably with a low RTD variability from one article to another.
• the present invention aims at providing a technical solution adapted to achieve at least one of the desirable results described above.
• an aerosol-generating article for producing an inhalable aerosol when heated, the aerosol-generating article comprising: a rod of aerosol-generating substrate; and a hollow tubular segment at a location downstream of the rod.
• the hollow tube segment is in longitudinal alignment with the rod and defines a cavity extending all the way from an upstream end of the hollow tubular segment to a downstream end of the hollow tubular segment.
• the hollow tubular segment has a length of at least about 10 millimetres. Further, the hollow tubular segment has a length of less than about 25 millimetres.
• the aerosol-generating article further comprises a ventilation zone at a location along the hollow tubular segment at less than 45 millimetres from an upstream end of the aerosol-generating article.
• the aerosol-generating article comprises a mouthpiece segment at a location downstream of the hollow tubular segment, the mouthpiece segment comprising a plug of filtration material.
• the hollow tubular segment comprises a tube formed from a polymeric material or a cellulosic material.
• the aerosol-generating article further comprises a wrapper circumscribing the rod, the tube and the mouthpiece segment.
• a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram/cubic millimetre.
• the rod of aerosol-generating substrate comprises at least an aerosol former, the rod of aerosol-generating substrate having an aerosol former content of at least about 10 percent on a dry weight basis.
• aerosol generating article is used herein to denote an article wherein an aerosol generating substrate is heated to produce an deliver inhalable aerosol to a consumer.
• aerosol generating substrate denotes a substrate capable of releasing volatile compounds 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.
• the localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke.
• 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 and aerosol generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol forming material.
• aerosol generating articles according to the invention find particular application in aerosol generating systems comprising an electrically heated aerosol generating device having an internal heater blade which is adapted to be inserted into the rod of aerosol generating substrate.
• Aerosol generating articles of this type are described in the prior art, for example, in EP 0822670 .
• aerosol generating device refers to a device comprising a heater element that interacts with the aerosol generating substrate of the aerosol generating article to generate an aerosol.
• tubular segment is used to denote an elongate element defining a lumen or airflow passage along a longitudinal axis thereof.
• tubular will be used in the following with reference to a tubular element having a substantially cylindrical cross-section and defining at least one airflow conduit establishing an uninterrupted fluid communication between an upstream end of the tubular element and a downstream end of the tubular element.
• tubular may be possible.
• the term “longitudinal” refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article.
• the terms “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use.
• transverse refers to the direction that is perpendicular to the longitudinal axis. Any reference to the "cross-section" of the aerosol-generating article or a component of the aerosol-generating article refers to the transverse cross-section unless stated otherwise.
• length denotes the dimension of a component of the aerosol-generating article in the longitudinal direction.
• length may be used to denote the dimension of the rod or of the elongate tubular elements in the longitudinal direction.
• thickness of a peripheral wall of the tubular element is used in the present specification to denote the minimum distance measured between the outer surface and the inner surface of the wall delimiting peripherally the tubular element.
• the distance at a given location is measured along a direction locally substantially perpendicular to the outer surface and the inner surface of the tubular element.
• the distance is measured along a substantially radial direction of the tubular element.
• 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 (for example, 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.
• the "thickness of a peripheral wall of the tubular element" is taken as the average value calculated on the basis of several values measured as the minimum distance between the outer surface and the inner surface of the wall at different locations along the length of the tubular element.
• a particularly significant parameter is the thickness of the peripheral wall of the tubular element at the location of the ventilation zone.
• air-impervious material is used throughout this specification to mean a material not allowing the passage of fluids, particularly air and smoke, through interstices or pores in the material. If the hollow tubular segment is formed of a material impervious to air and aerosol particles, air and aerosol particles drawn through the hollow tubular segment are forced to flow through the airflow conduit internally defined by the hollow tubular segment, but cannot flow across the peripheral wall of the hollow tubular segment.
• homogenised tobacco material encompasses any tobacco material formed by the agglomeration of particles of tobacco material.
• Sheets or webs of homogenised tobacco material are formed by agglomerating particulate tobacco obtained by grinding or otherwise powdering of one or both of tobacco leaf lamina and tobacco leaf stems.
• homogenised tobacco material may comprise a minor quantity of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco.
• the sheets of homogenised tobacco material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.
• 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.
• ventilation level is used throughout the present specification to denote a volume ratio between of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer.
• the aerosol-generating article of the present invention comprises a rod of aerosol-generating substrate, and a hollow tubular segment at a location downstream of the rod. These two elements are longitudinally aligned.
• the rod of aerosol-generating substrate comprises at least an aerosol former.
• the rod of aerosol-generating substrate has an aerosol former content of at least about 10 percent on a dry weight basis.
• the hollow tubular segment defines a cavity that extends all the way to from an upstream end of the hollow tubular segment to a downstream end of the hollow tubular segment, and has a length of less than about 25 millimetres.
• a ventilation zone is provided at a location along the hollow tubular segment.
• ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram/cubic millimetre.
• the overall structural complexity of the article may be significantly reduced compared with existing aerosol-generating articles. This advantageously simplifies the manufacturing process and reduces the complexity of the making and combining apparatus required for implementing the manufacturing process.
• One such aerosol-generating article does not comprise an aerosol-cooling element adapted to lower the temperature of a stream of aerosol drawn through the aerosol-generating article - as is the case, for example, with the aerosol-generating articles described in international patent application WO 2013/120565 .
• the inventors have found that a satisfactory cooling of the stream of aerosol generated upon heating the article and drawn through the hollow tubular element is achieved by providing a ventilation zone at a location along the hollow tubular segment. Further, the inventors have surprisingly found that, by utilising a hollow tubular segment having a length of less than about 25 millimetres and wherein a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 1 milligram/cubic millimetre, it may be possible to counter the effects of the increased aerosol dilution caused by the admission of ventilation air into the article.
• the overall proportion of the aerosol particulate phase to the aerosol gas phase may be enhanced compared with existing, non-ventilated aerosol-generating articles.
• a cooling chamber is effectively provided within which the condensation of aerosol particles upstream of a mouth end of the article may be favoured, as nucleation phenomena are enhanced by slowing down the flow of the aerosol stream.
• hollow tubular segments falling within the ranges described above provide sufficient structural strength to the article and maintain the rod of aerosol-generating article at a predetermined distance from a mouth end of the article. Accordingly, such hollow tubular segments provide a sufficiently long chamber for the aerosol stream to flow in, and therefore enough time is made available during use for the temperature of the volatilised species to be reduced and for nucleation of aerosol particles to take place. Further, a relatively short hollow tubular segment as in aerosol-generating articles in accordance with the invention has been found to enable good aerosol nucleation whilst, at the same time, not presenting to the aerosol particles too large a surface area on which they may condense.
• the cross-sectional surface area of the cavity of the hollow tubular segment may be maximised, whilst at the same time ensuring that the hollow tubular segment has the necessary structural strength to prevent a collapse of the aerosol-generating article as well as to provide some support to the rod of aerosol-generating substrate, and that the RTD of the hollow tubular segment is minimised.
• Greater values of cross-sectional surface area of the cavity of the hollow tubular segment are understood to be associated with a reduced speed of the aerosol stream travelling along the aerosol-generating article, which is also expected to favour aerosol nucleation.
• a hollow tubular segment having a low thickness such as a thickness below 1.5 millimetres, it is possible to substantially prevent diffusion of the ventilation air prior to its contacting and mixing with the stream of aerosol, which is also understood to further favour nucleation phenomena.
• a more controllably localised cooling of the stream of volatilised species it is possible to enhance the effect of cooling on the formation of new aerosol particles.
• the inventors have surprisingly found how the favourable effect of enhanced nucleation may significantly counter the less desirable effects of dilution, such that satisfactory values of aerosol delivery are consistently achieved with aerosol-generating articles in accordance with the invention.
• This is particularly advantageous with "short" aerosol-generating articles, such as ones wherein a 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 wherein an 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.
• a 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 wherein an 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 mill
• the hollow tubular element substantially does not contribute to the RTD of the aerosol-generating article
• the overall RTD of the article can 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 filtration material of the mouthpiece segment, in those embodiments where a mouthpiece segment is present. This enables the manufacture of aerosol-generating substrates having a predetermined RTD consistently and with great precision, such that satisfactory levels of RTD can be provided for the consumer even in the presence of ventilation.
• Aerosol-generating articles in accordance with the invention can be made in a continuous process which can be efficiently carried out at high speed, and can be conveniently manufactured on existing production lines for the manufactured of heated aerosol generating articles without requiring extensive modifications of the manufacturing equipment.
• the rod of aerosol generating substrate preferably has an external diameter that is approximately equal to the external diameter of the aerosol generating article.
• the rod of aerosol generating substrate has an external diameter of at least 5 millimetres.
• the rod of aerosol generating substrate may have an external diameter of between about 5 millimetres and about 12 millimetres, for example of between about 5 millimetres and about 10 millimetres or of between about 6 millimetres and about 8 millimetres.
• the rod of aerosol generating substrate has an external diameter of 7.2 millimetres, to within 10 percent.
• the rod of aerosol generating substrate may have a length of between about 5 millimetres and about 100 mm.
• the rod of aerosol generating substrate has a length of at least about 5 millimetres, more preferably at least about 7 millimetres.
• 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.
• the rod of aerosol generating substrate has a length of less than about 35 millimetres, more preferably less than 25 millimetres, even more preferably less than about 20 millimetres.
• the rod of aerosol generating substrate may have a length of about 10 millimetres.
• the rod of aerosol generating substrate has a length of about 12 millimetres.
• Sheets or webs of homogenised tobacco material for use in the aerosol-generating substrate may comprise one or more intrinsic binders, that is tobacco endogenous binders, one or more extrinsic binders, that is tobacco exogenous binders, or a combination thereof to help agglomerate the particulate tobacco.
• sheets of homogenised tobacco material for use in the 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 extrinsic binders for inclusion in sheets or webs of homogenised tobacco material for use in the aerosol-generating substrate include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins; and combinations thereof.
• gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum
• cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl
• the sheets or webs of homogenised tobacco material comprise an aerosol former.
• aerosol former describes any suitable known compound or mixture of compounds that, in use, facilitates formation of an aerosol and that is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article.
• Suitable aerosol-formers include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.
• polyhydric alcohols such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerine
• esters of polyhydric alcohols such as glycerol mono-, di- or triacetate
• aliphatic esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.
• Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as propylene glycol, triethylene glycol, 1,3-butanediol and, most preferred, glycerine.
• the sheets or webs of homogenised tobacco material may comprise a single aerosol former.
• the sheets or webs of homogenised tobacco material may comprise a combination of two or more aerosol formers.
• the sheets or webs of homogenised tobacco material have an aerosol former content of greater than 10 percent on a dry weight basis.
• the sheets or webs of homogenised tobacco material have an aerosol former content of greater than 12 percent on a dry weight basis. More preferably, the sheets or webs of homogenised tobacco material have an aerosol former content of greater than 14 percent on a dry weight basis. Even more preferably the sheets or webs of homogenised tobacco material have an aerosol former content of greater than 16 percent on a dry weight basis.
• the sheets of homogenised tobacco material may have an aerosol former content of between approximately 10 percent and approximately 30 percent on a dry weight basis.
• the sheets or webs of homogenised tobacco material have an aerosol former content of less than 25 percent on a dry weight basis.
• the sheets of homogenised tobacco material have an aerosol former content of approximately 20 percent on a dry weight basis.
• Sheets or webs of homogenised tobacco for use in the aerosol-generating article of the present invention may be made by methods known in the art, for example the methods disclosed in International patent application WO-A-2012/164009 A2 .
• sheets of homogenised tobacco material for use in the aerosol-generating article are formed from a slurry comprising particulate tobacco, guar gum, cellulose fibres and glycerine by a casting process.
• homogenised tobacco material in a rod for use in an aerosol-generating article may include a plurality of stacked sheets of homogenised tobacco material, a plurality of elongate tubular elements formed by winding strips of homogenised tobacco material about their longitudinal axes, etc.
• the rod of aerosol-generating substrate may comprise a non-tobacco-based, nicotine-bearing material, such as a sheet of sorbent non-tobacco material loaded with nicotine (for example, in the form of a nicotine salt) and an aerosol-former. Examples of such rods are described in the international application WO-A-2015/052652 .
• the rod of aerosol-generating substrate may comprise a non-tobacco plant material, such as an aromatic non-tobacco plant material.
• the aerosol-generating substrate is preferably circumscribed by a wrapper.
• the wrapper may be formed of a porous or non-porous sheet material.
• the wrapper may be formed of any suitable material or combination of materials.
• the wrapper is a paper wrapper.
• Aerosol-generating articles in accordance with the present invention comprise a mouthpiece segment at a location downstream of the hollow tubular segment, preferably in end-to-end abutment with the hollow tubular segment.
• the cavity of the hollow tubular segment extends all the way to an upstream end of the mouthpiece segment.
• the mouthpiece typically 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 such as, for example, cellulose acetate tow, viscose fibres, polyhydroxyalkanoates (PHA) fibres, polylactic acid (PLA) fibres and paper; adsorbents such as, for example, activated alumina, zeolites, molecular sieves and silica gel; and combinations thereof.
• the plug of filtration material may further comprise one or more aerosol-modifying agent.
• Suitable aerosol-modifying agents are known in the art and include, but are not limited to, flavourants such as, for example, menthol.
• the mouthpiece may further comprise a mouth end recess downstream of the plug of filtration material.
• the mouthpiece may comprise a hollow tube arranged in longitudinal alignment with, and immediately downstream of the plug of filtration material, the hollow tube forming a cavity at the mouth end that is open to the outer environment at the downstream end of the mouthpiece and of the aerosol-generating article.
• a length of the mouthpiece is preferably at least about 4 millimetres, more preferably at least about 6 millimetres, even more preferably at least about 8 millimetres.
• a length of the mouthpiece is preferably less than 25 millimetres, more preferably less than 20 millimetres, even more preferably less than 15 millimetres.
• a length of the mouthpiece is from about 4 millimetres to about 25 millimetres, more preferably from about 6 millimetres to about 20 millimetres.
• a length of the mouthpiece is about 7 millimetres.
• a length of the mouthpiece is about 12 millimetres.
• a similar segment of filtration material may alternatively or additionally be provided at a location between the rod of aerosol-generating substrate and the hollow tubular segment.
• the hollow tubular segment is preferably an annular tube delimiting and defining an air gap within the aerosol-generating article.
• the hollow tubular segment provides a chamber for the volatilised aerosol components released upon heating the aerosol-generating substrate to accumulate and flow in. As described briefly above, this chamber extends longitudinally all the way from an upstream end of the hollow tubular segment to a downstream end of the hollow tubular segment.
• the hollow tubular segment maintains the rod of aerosol-generating substrate at a predetermined distance from the mouth end of the article and provides an elongate airflow conduit for the aerosol to form and flow towards the mouth end of the article.
• a thermal gradient is established along this airflow conduit.
• a temperature differential is provided, such that a temperature of the volatilised aerosol components entering the hollow tubular segment at the upstream end is greater than a temperature of the volatilised aerosol components exiting the hollow tubular segment at the downstream end (that is, the upstream end of the mouthpiece, where a mouthpiece is present).
• the hollow tubular segment is required to withstand any axial compressive load or bending moment that may be applied on the hollow tubular segment during manufacture of the aerosol-generating article. Further, the hollow tubular segment is required to impart structural strength to the aerosol-generating article, such that it can easily be handled by the consumer and inserted into an aerosol-generating device for use. On the other hand, it is desirable that the overall volume of the chamber internally defined by the hollow tubular element is as large as possible, so as to favour the formation of aerosol and enhance the delivery of aerosol to the consumer.
• a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 1 milligrams/cubic millimetres. More preferably, a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 0.5 milligrams/cubic millimetres. Even more preferably, a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 0.2 milligrams/cubic millimetres. In particularly preferred embodiments, a ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is less than 0.1 milligrams/cubic millimetres.
• the volume of the cavity 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 mouth end of the article.
• the hollow tubular segment has an internal equivalent diameter of 7 millimetres and is formed from a wrapper having a basis weight of 110 gsm, with a weight of 2.5 milligram/millimetre.
• the ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is about 0.065 milligrams/cubic millimetres.
• a hollow tubular segment has an internal equivalent diameter of 5.3 millimetres may be provided as a cellulose acetate tube with a weight of 9.5 milligram/millimetre.
• the ratio between a weight of the hollow tubular segment and a volume of the internal cavity defined by the hollow tubular segment is about 0.43 milligrams/cubic millimetres.
• a thickness of a peripheral wall of the hollow tubular segment is less than 1.5 millimetre.
• the thickness of the peripheral wall of the hollow tubular segment is less than 1250 micrometres, more preferably less than 1000 micrometres, even more preferably less than 900 micrometres. In particularly preferred embodiments, the thickness of the peripheral wall of the hollow tubular segment is less than 800 micrometres.
• the thickness of the peripheral wall of the hollow tubular segment is at least about 100 micrometres. Preferably, the thickness of the peripheral wall of the hollow tubular segment is at least about 200 micrometres.
• an equivalent internal diameter of the hollow tubular segment is at least about 4 millimetres.
• the term "equivalent internal diameter” is used herein to denote the diameter of a circle having the same surface area of a cross-section of the airflow conduit internally defined by the hollow tubular segment.
• a cross-section of the airflow conduit may have any suitable shape.
• a circular cross-section is preferred - that is, the hollow tubular segment is effectively a cylindrical tube. In that case, the equivalent internal diameter of the hollow tubular segment effectively coincides with the internal diameter of the cylindrical tube.
• an equivalent internal diameter of the hollow tubular segment is at least about 5 millimetres, even more preferably at least about 5.25 millimetres, most preferably at least about 5.5 millimetres. In some embodiments, an equivalent internal diameter of the hollow tubular segment is at least about 6 millimetres or at least about 6.5 millimetres or at least about 7 millimetres.
• an equivalent internal diameter of the hollow tubular segment is preferably less than about 10 millimetres. More preferably, an equivalent internal diameter of the hollow tubular segment is less than about 9.5 millimetres, even more preferably less than 9 millimetres.
• the equivalent internal diameter of the hollow tubular segment is measured at the location of the ventilation zone.
• the equivalent internal diameter of the hollow tubular segment is substantially constant along the length of the hollow tubular segment. In other embodiments, the equivalent internal diameter of the hollow tubular segment may vary along the length of the hollow tubular segment.
• aerosol-generating articles in accordance with the invention that comprise a hollow tubular segment having an equivalent internal diameter within the ranges described above could provide particularly satisfactory values of aerosol delivery.
• aerosol stream flowing along a hollow tubular segment having an equivalent internal diameter falling within the ranges described above is caused to flow at a relatively low speed when the incoming flow of cooler ventilation air is received into and mixed with the aerosol stream. Because the aerosol stream advances relatively slowly along the hollow tubular segment, the favourable impact of cooling on aerosol nucleation is expected to be maximised under such conditions.
• an equivalent internal diameter of the hollow tubular segment is substantially constant along the length of the hollow tubular segment.
• the cross-sectional surface area of the hollow tubular segment may vary along the length of the hollow tubular segment.
• the equivalent internal diameter is measured at the location of the ventilation zone.
• aerosol-generating articles in accordance with the present invention comprise a ventilation zone at a location along the hollow tubular segment.
• the ventilation zone is provided at a location less than about 18 millimetres from an upstream end of the hollow tubular segment.
• a distance between the ventilation zone and an upstream end of the hollow tubular segment is less than about 15 millimetres. Even more preferably, a distance between the ventilation zone and upstream end of the hollow tubular segment is less than about 10 millimetres.
• a distance between the ventilation zone and an upstream end of the hollow tubular segment is preferably at least 2 millimetres. More preferably, a distance between the ventilation zone and an upstream end of the hollow tubular segment is at least about 4 millimetres. Even more preferably, a distance between the ventilation zone and an upstream end of the hollow tubular segment is at least about 6 millimetres.
• the ventilation zone is preferably provided at a location along the hollow tubular segment at least 2 millimetres from the upstream end of the mouthpiece.
• the ventilation zone is provided at a location along the hollow tubular segment at least 4 millimetres from the upstream end of the mouthpiece.
• the ventilation zone is provided at a location along the hollow tubular segment at least 6 millimetres from the upstream end of the mouthpiece.
• the ventilation zone As the mixture of air and aerosol particles flowing through the aerosol-generating article reaches the ventilation zone, external air drawn into the hollow tubular segment via the ventilation zone is mixed with the aerosol. This rapidly reduces the temperature of the aerosol mixture whilst partially diluting the mixture of air and aerosol particles.
• a cooling chamber is effectively provided immediately upstream of the mouthpiece, wherein nucleation and growth of aerosol particles is advantageously favoured.
• the diluting effect of the ventilation air admitted into the hollow tubular segment is at least partly countered, which advantageously enables the provision of aerosol delivery levels that are satisfactory for the consumer.
• a ratio between the distance between the ventilation zone and an upstream end of the hollow tubular segment and an equivalent internal diameter of the hollow tubular segment at the location of the ventilation zone is less than 4.
• a ratio between the distance between the ventilation zone and an upstream end of the hollow tubular segment and an equivalent internal diameter of the hollow tubular segment at the location of the ventilation zone is less than 3.5.
• a ratio between the distance between the ventilation zone and an upstream end of the hollow tubular segment and an equivalent internal diameter of the hollow tubular segment at the location of the ventilation zone is less than 3.
• a ratio between the distance between the ventilation zone and an upstream end of the hollow tubular segment and an equivalent internal diameter of the hollow tubular segment at the location of the ventilation zone is less than 2.5.
• a ratio between the distance between the ventilation zone and an upstream end of the hollow tubular segment and an equivalent internal diameter of the hollow tubular segment at the location of the ventilation zone is less than 2, more preferably less than 1.5, even more preferably less than 1.2.
• the ventilation zone is provided at a location along the hollow tubular segment at least 10 millimetres from a downstream end of the aerosol-generating article. More preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 12 millimetres from a downstream end of the aerosol-generating article. Even more preferably, the ventilation zone is provided at a location along the hollow tubular segment at least 15 millimetres from a downstream end of the aerosol-generating article. This is advantageous in that is ensures that, during use, the ventilation zone is not occluded by the consumer's lips.
• the ventilation zone is preferably at a location along the hollow tubular segment less than 25 millimetres from a downstream end of the aerosol-generating article. More preferably, the ventilation zone is at a location along the hollow tubular segment less than 20 millimetres from a downstream end of the aerosol-generating article. This advantageously ensures that during use, when the aerosol-generating article is received within a heating chamber of an electrically heated aerosol-generating device, the ventilation zone is effectively at a location along the hollow tubular segment that projects outside of the heating chamber, such that external cooling air can easily be drawn into the hollow tubular segment.
• the ventilation zone is provided at a location along the hollow tubular segment from about 10 millimetres to about 25 millimetres from a downstream end of the aerosol-generating device, more preferably from about 12 millimetres to about 20 millimetres from a downstream end of the aerosol-generating device. In an exemplary embodiment, the ventilation zone is provided at a location along the hollow tubular segment 18 millimetres from the downstream end of the aerosol-generating device. In another exemplary embodiment, the ventilation zone is provided at a location along the hollow tubular segment 13 millimetres from the downstream end of the aerosol-generating device.
• the aerosol-generating article may typically have a ventilation level of at least about 10 percent, preferably at least about 20 percent.
• 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. In addition, or as an alternative, 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 from about 30 percent to about 60 percent. More preferably, the aerosol-generating article has a ventilation level from about 35 percent to about 50 percent. In some particularly preferred embodiments, the aerosol-generating article has a ventilation level of about 40 percent.
• the inventors have found that the temperature drop caused by the admission of cooler, external air into the hollow tubular segment via the ventilation zone may have an advantageous effect on the nucleation and growth of aerosol particles.
• Formation of an aerosol from a gaseous mixture containing various chemical species depends on a delicate interplay between nucleation, evaporation, and condensation, as well as coalescence, all the while accounting for variations in vapour 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 stay coherent for long times with sufficient probability (for example, a probability of one half).
• These molecules represent some kind of a critical, threshold molecule clusters among transient molecular aggregates, meaning that, on average, smaller molecule clusters are likely to disintegrate rather quickly into the gas phase, while larger clusters are, on average, likely to grow.
• Such critical cluster is identified as the key nucleation core from which droplets are expected to grow due to condensation of molecules from the vapour. It is assumed that virgin droplets that just nucleated emerge with a certain original diameter, and then may grow by several orders of magnitude. This is facilitated and may be enhanced by rapid cooling of the surrounding vapour, which induces condensation. In this connection, it helps to bear in mind that evaporation and condensation are two sides of one same mechanism, namely gas-liquid mass transfer. While evaporation relates to net mass transfer from the liquid droplets to the gas phase, condensation is net mass transfer from the gas phase to the droplet phase. Evaporation (or condensation) will make the droplets shrink (or grow), but it will not change the number of droplets.
• the temperature and rate of cooling can play a critical role in determining how the system responds.
• different cooling rates may lead to significantly different temporal behaviours as concerns the formation of the liquid phase (droplets), because the nucleation process is typically nonlinear.
• nucleation burst a strong, short-lived increase in this growth.
• This nucleation burst would appear to be more significant at lower temperatures.
• higher cooling rates may favour an earlier onset of nucleation.
• a reduction of the cooling rate would appear to have a favourable effect on the final size that the aerosol droplets ultimately reach.
• the rapid cooling induced by the admission of external air into the hollow tubular segment via the ventilation zone can be favourably used to favour nucleation and growth of aerosol droplets.
• the admission of external air into the hollow tubular segment has the immediate drawback of diluting the aerosol stream delivered to the consumer.
• the inventors have surprisingly found that the diluting effect on the aerosol - which can be assessed by measuring, in particular, the effect on the delivery of glycerin included in the aerosol-generating substrate as the aerosol former - is advantageously minimised when the ventilation level is between 30 percent and 50 percent. In particular, ventilation levels between 35 percent and 42 percent have been found to lead to particularly satisfactory values of glycerin delivery.
• the inventors have found that in aerosol-generating articles in accordance with the invention the cooling and diluting effect caused by the admission of ventilation air at the location along the conduit defined by the hollow tubular segment described above has a surprising reducing effect on the generation and delivery of phenol-containing species.
• the ventilation zone may comprise one or more rows of perforations formed through the peripheral wall of the hollow tubular segment.
• the ventilation zone comprises only one rows of perforations. This is understood to be advantageous in that, by concentrating the cooling effect brought about by ventilation over a short portion of the cavity defined by the hollow tube segment, it may be possible to further enhance aerosol nucleation. This is because a faster and more drastic cooling of the stream of volatilised species is expected to particularly favour the formation of new nuclei of aerosol particles.
• the one or more rows of perforations are arranged circumferentially around the wall of the hollow tube.
• 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.
• adjacent rows of perforations may be longitudinally spaced from one another by a distance of between about 0.25 millimetres and 0.75 millimetres.
• An equivalent diameter of at least one of the ventilation perforations is preferably at least about 100 micrometres.
• an equivalent diameter of at least one of the ventilation perforations is at least about 150 micrometres. Even more preferably, an equivalent diameter of at least one of the ventilation perforations is at least about 200 micrometres.
• an equivalent diameter of at least one of the ventilation perforations is preferably less than about 500 micrometres. More preferably, an equivalent diameter of at least one of the ventilation perforations is less than about 450 micrometres. Even more preferably, an equivalent diameter of at least one of the ventilation perforations is less than about 400 micrometres.
• equivalent diameter is used herein to denote the diameter of a circle having the same surface area of a cross-section of the ventilation perforation.
• a 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. As an alternative, 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 external air admitted into the hollow tubular segment when the consumer draws on the mouth end of the aerosol-generating article during use. As such, it is advantageously possible to adjust the ventilation level of the aerosol-generating article.
• a length of the hollow tubular segment is at least about 10 millimetres. More preferably, a length of the hollow tubular segment is at least about 15 millimetres. In addition, or as an alternative, a length of the hollow tubular segment is preferably less than about 30 millimetres. More preferably, a length of the hollow tubular segment is less than about 25 millimetres. Even more preferably, a length of the hollow tubular segment is less than about 20 millimetres. In some preferred embodiments, a length of the hollow tubular segment is from about 10 millimetres to about 30 millimetres, more preferably from about 12 millimetres to about 25 millimetres, even more preferably from about 15 millimetres to about 20 millimetres. By way of example, in a particularly preferred embodiment the length of the hollow tubular segment is about 18 millimetres. In another particularly preferred embodiment the length of the hollow tubular segment is about 13 millimetres.
• 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 aerosol-generating article.
• a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is typically at least about 2 millimetres.
• a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is at least about 4 millimetres. More preferably, a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is at least about 5 millimetres. Even more preferably, a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is at least about 10 millimetres. In some, particularly preferred embodiments, a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate may be at least about 15 millimetres.
• a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is preferably less than about 35 millimetres. More preferably, a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is less than about 30 millimetres. Even more preferably, a distance between the ventilation zone and a downstream end of the rod of aerosol-generating substrate is less than about 25 millimetres.
• the ventilation zone divides the cavity internally defined by the hollow tubular segment into an upstream sub-cavity, which extends longitudinally from an upstream end of the hollow tubular segment to the location of the ventilation zone, and a downstream sub-cavity, which extends longitudinally from the location of the ventilation zone to the downstream end of the hollow tubular segment.
• an upstream sub-cavity which extends longitudinally from an upstream end of the hollow tubular segment to the location of the ventilation zone
• a downstream sub-cavity which extends longitudinally from the location of the ventilation zone to the downstream end of the hollow tubular segment.
• the aerosol stream and the ventilation air rapidly mix up, which causes a quick cooling of the volatilised species of the aerosol stream and so favours the nucleation of new aerosol particles and the growth of already existing aerosol particles as the aerosol advances towards the mouth end of the article.
• a ratio between a length of the upstream cavity and a length of the downstream cavity is less than 1.5. More preferably, a ratio between a length of the upstream cavity and a length of the downstream cavity is less than 1. Even more preferably, a ratio between a length of the upstream cavity and a length of the downstream cavity is less than 0.67.
• a ratio between a length of the upstream cavity and a length of the downstream cavity is preferably at least about 0.15. More preferably, a ratio between a length of the upstream cavity and a length of the downstream cavity is preferably at least about 0.2. Even more preferably, a ratio between a length of the upstream cavity and a length of the downstream cavity is preferably at least about 0.35.
• the ventilation zone divides the aerosol-generating article in two sections, upstream and downstream of the location of the ventilation zone, respectively.
• a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is less than 2.5. More preferably, a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is less than 2. Even more preferably, a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is less than 1.5. In particularly preferred embodiments, a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is less than 1.
• a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is preferably at least about 0.25. More preferably, a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is at least about 0.33. Even more preferably, a ratio between a length of the upstream section of the aerosol-generating article and a length of the downstream section of the aerosol-generating article is at least about 0.5.
• the invention may also provide a pack comprising ten or more aerosol-generating articles as described above, wherein a difference between an RTD of the aerosol-generating article having the highest RTD among the at least ten aerosol-generating articles and an RTD of the aerosol-generating article having the lowest RTD among the at least ten aerosol-generating articles is less than 10 mm H 2 O (about 100 Pascal).
• the difference between an RTD of the aerosol-generating article having the highest RTD among the at least ten aerosol-generating articles and an RTD of the aerosol-generating article having the lowest RTD among the at least ten aerosol-generating articles is less than 9 mm H 2 O (about 90 Pascal, more preferably less than 8 mm H 2 O (about 80 Pascal), even more preferably less than 7 mm H 2 O (about 70 Pascal).
• the aerosol-generating article 10 shown in Figure 1 comprises 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 in end-to-end, longitudinal alignment and are circumscribed by a 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 opposite end of the article to 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 the rod of aerosol-generating substrate.
• the rod of aerosol-generating substrate 12 has a length of about 12 millimetres and a diameter of about 7 millimetres.
• the rod 12 is cylindrical in shape and has a substantially circular cross-section.
• the rod 12 comprises a gathered sheet of homogenised tobacco material.
• the sheet of homogenised tobacco material comprises 10 percent by weight on a dry basis of glycerine.
• the hollow cellulose acetate tube 14 has a length of about 8 millimetres and a thickness of 1 millimetre.
• the mouthpiece segment 18 comprises a plug of cellulose acetate tow of 8 denier per filament and has a length of about 7 millimetres.
• the hollow tubular segment 14 is provided as a cylindrical tube having a length of about 18 millimetres and a thickness of the tube wall is about 100 micrometres.
• the hollow tubular segment 16 may for example be formed from a paper having a basis weight of 110 gsm and has a weight of 45 milligrams (that is, 2.5 milligrams/millimetre of length).
• An equivalent internal diameter of the hollow tubular segment 16 is about 7 millimetres.
• a volume of the cavity internally defined by the hollow tubular segment 16 is about 693 cubic millimetres.
• a ratio between the weight of the hollow tubular segment and the volume of the internal cavity defined by the hollow tubular segment 16 is about 0.065.
• the aerosol-generating article 10 comprises a ventilation zone 26 provided at about 5 millimetres from an upstream end of the mouthpiece segment 18.
• the ventilation zone 26 is at about 12 millimetres from the downstream end of the aerosol-generating article, and about 13 millimetres from the upstream end of the hollow tubular segment.
• the ventilation zone 26 is at about 21 millimetres from a downstream end of the rod 12.
• FIG. 2 illustrates another example of an aerosol-generating article in accordance with the invention.
• the aerosol-generating article 30 of Figure 2 has the same structure of the aerosol-generating article 10 of Figure 1 and differs from the aerosol-generating article 10 substantially only in the length of certain components, and will be described below only insofar as it differs from the aerosol-generating article 10.
• the same reference numerals will be used, wherever possible, for corresponding components having the same structural or functional function.
• the rod 12 and the hollow cellulose acetate tube 14 have the same length as in the aerosol-generating article 10 of Figure 1 .
• the mouthpiece segment comprises a plug of cellulose acetate tow of 11 denier per filament and having a length of about 12 millimetres, and a hollow tubular segment 14 having a length of about 13 millimetres.
• the ventilation zone 26 is provided at about 6 millimetres from the upstream end of the mouthpiece segment 18, and at about 7 millimetres from the upstream end of the hollow tubular segment. Thus, the ventilation zone 26 is at about 15 millimetres from a downstream end of the rod 12.
• the hollow tubular segment 16 may for example be provided as a cylindrical tube of cellulose acetate having a length of about 18 millimetres and a peripheral wall thickness of about 1 millimetre, with a weight of 171 milligrams (that is, 9.5 milligrams/millimetre of length).
• FIG. 3 illustrates yet another example of an aerosol-generating article in accordance with the invention.
• the aerosol-generating article 40 of Figure 3 differs structurally from the aerosol-generating articles 10 of Figure 1 and 30 of Figure 2 in that it does not include a hollow cellulose acetate tube as a support element. Accordingly, the lengths of the three main components are also different. In the following the same reference numerals will be used, wherever possible, for corresponding components having the same structural or functional function.
• the rod 12 has a length of about 12 millimetres
• the hollow tubular segment 14 has a length of about 26 millimetres
• the mouthpiece segment 18 comprises a plug of cellulose acetate tow has a length of about 12 millimetres and 11 denier per filament.
• the ventilation zone 26 is provided at about 5 millimetres from the upstream end of the mouthpiece segment 18, and at about 21 millimetres from the upstream end of the hollow tubular segment, which in this embodiment coincides with the downstream end of the rod 12.
• EXAMPLE 1 This experiment is performed to assess the effect of incorporation of a hollow tubular segment wherein a ventilation zone is provided at a location along the hollow tubular segment in accordance with the present invention. The experiment investigates the effect of the ventilation level on the delivery of nicotine and aerosol former (glycerin). A comparative measurement with a reference aerosol-generating article without ventilation is also provided.
• Article A is an aerosol-generating article formed of: a rod of aerosol-generating substrate comprising a gathered sheet of homogenised tobacco material and about 18 percent on a dry weight basis of glycerin, the rod having a length of 12 millimetres; a support element in the form of a hollow cellulose acetate tube in alignment with and immediately downstream of the rod, the support element having a length of 8 millimetres; a hollow tubular segment in the form of a cardboard tube in alignment with and immediately downstream of the rod, the hollow tubular segment having a length of 13 millimetres; a mouthpiece segment of filtration material in alignment with and immediately downstream of the hollow tubular segment, the mouthpiece segment having a length of 12 millimetres.
• a ventilation zone is provided at a location along the hollow tubular segment at 18 millimetres from a downstream end of the mouthpiece segment.
• a level of ventilation of aerosol-generating article A is 30 percent.
• Article B is a reference aerosol-generating article having the same structure of article A, but without the ventilation zone. Thus, a level of ventilation of aerosol-generating article B is 0 percent.
• Nicotine and glycerin deliveries are measured by gas chromatography/time-of-flight mass spectrometry (GC/MS-TOF) on the nicotine and glycerin collected on a Cambridge filter pad. Runs were performed as described in example 1

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