Aerosol-generating article having an aerosol-cooling element

Abstract

An aerosol-generating article is provided, including a plurality of elements assembled in the form of a rod, the elements including an aerosol-forming substrate and an aerosol-cooling element located downstream from the aerosol-forming substrate. The aerosol-cooling element includes a plurality of longitudinally extending channels and has a porosity of between 50% and 90% in the longitudinal direction. The aerosol-cooling element may have a total surface area of between about 300 mm.sup.2 per mm length and about 1000 mm.sup.2 per mm length. An aerosol passing through the aerosol-cooling element is cooled, and in some embodiments, water is condensed within the aerosol-cooling element.

Claims

1. A heated aerosol-generating article, comprising: a plurality of elements assembled in the form of a rod by means of a paper wrapper, the plurality of elements including an aerosol-forming substrate, an aerosol-cooling element located downstream from the aerosol-forming substrate within the rod, and a mouthpiece filter located downstream from the aerosol-cooling element within the rod, wherein a first end of the mouthpiece filter forms a mouth end of the rod and the aerosol-cooling element is disposed adjacent a second end of the mouthpiece filter, the rod further comprises a spacer element located between the aerosol-forming substrate and the aerosol-cooling element within the rod, the aerosol-forming substrate being disposed immediately adjacent to the spacer element, outer surfaces of each of the aerosol-forming substrate, the spacer element, the aerosol-cooling element, and the mouthpiece filter abut an inner surface of the paper wrapper, the aerosol-forming substrate is formed from a homogenised tobacco material having an aerosol former content of between 5% and 30% by weight on a dry weight basis, and in which the aerosol-cooling element is formed from a polymeric sheet that has been crimped such that the polymeric sheet has a plurality of parallel ridges and corrugations that, in the heated aerosol-generating article, extend in a longitudinal direction therein, and gathered such that the aerosol-cooling element comprises a plurality of longitudinally extending channels and has a longitudinal porosity of between 50% and 90% in the longitudinal direction, the longitudinal porosity being derived from a ratio of a cross-sectional area of material forming the aerosol-cooling element and an internal cross-sectional area of the heated aerosol-generating article at a portion containing the aerosol-cooling element, the aerosol-cooling element has a total surface area of between 300 mm.sup.2 per mm length of the aerosol-cooling element and 1000 mm.sup.2 per mm length of the aerosol-cooling element, the external diameter of the article is between 5 mm and 12 mm, wherein the aerosol-cooling element comprises a polymeric sheet material formed of polylactic acid, a temperature of a stream of aerosol drawn through the aerosol-cooling element is lowered by more than 20° C., and a water vapor content of an aerosol stream drawn through the aerosol-cooling element is lowered by between about 20% and about 90%.

2. The heated aerosol-generating article according to claim 1, wherein the aerosol-cooling element is between about 7 mm and about 28 mm in length.

3. The heated aerosol-generating article according to claim 1, wherein the aerosol former includes glycerine and propylene glycol.

4. The heated aerosol-generating article according to claim 1, wherein the spacer element is a tube.

5. The heated aerosol-generating article according to claim 4, wherein the tube is a hollow acetate tube.

Description

(1) A specific embodiment will now be described with reference to the figures, in which;

(2) FIG. 1 is a schematic cross-sectional diagram of a first embodiment of an aerosol-generating article;

(3) FIG. 2 is a schematic cross-sectional diagram of a second embodiment of an aerosol-generating article;

(4) FIG. 3 is a graph illustrating puff per puff mainstream smoke temperature for two different aerosol-generating articles;

(5) FIG. 4 is a graph comparing intra puff temperature profiles for two different aerosol-generating articles;

(6) FIG. 5 is a graph illustrating puff per puff mainstream smoke temperature for two different aerosol-generating articles;

(7) FIG. 6 is a graph illustrating puff per puff mainstream nicotine levels for two different aerosol-generating articles;

(8) FIG. 7 is a graph illustrating puff per puff mainstream glycerine levels for two different aerosol-generating articles;

(9) FIG. 8 is a graph illustrating puff per puff mainstream nicotine levels for two different aerosol-generating articles;

(10) FIG. 9 is a graph illustrating puff per puff mainstream glycerine levels for two different aerosol-generating articles;

(11) FIG. 10 is a graph comparing mainstream nicotine levels between an aerosol-generating article and a reference cigarette;

(12) FIGS. 11A, 11B and 11C illustrate dimensions of a crimped sheet material and a rod that may be used to calculate the longitudinal porosity of the aerosol-cooling element.

(13) FIG. 1 illustrates an aerosol-generating article 10 according to an embodiment. The aerosol-generating article 10 comprises four elements, an aerosol-forming substrate 20, a hollow cellulose acetate tube 30, an aerosol-cooling element 40, and a mouthpiece filter 50. These four elements are arranged sequentially and in coaxial alignment and are assembled by a cigarette paper 60 to form a rod 11. The rod 11 has a mouth-end 12, which a user inserts into his or her mouth during use, and a distal end 13 located at the opposite end of the rod 11 to the mouth end 12. Elements located between the mouth-end 12 and the distal end 13 can be described as being upstream of the mouth-end 12 or, alternatively, downstream of the distal end 13.

(14) When assembled, the rod 11 is about 45 millimetres in length and has an outer diameter of about 7.2 millimetres and an inner diameter of about 6.9 millimetres.

(15) The aerosol-forming substrate 20 is located upstream of the hollow tube 30 and extends to the distal end 13 of the rod 11. In one embodiment, the aerosol-forming substrate 20 comprises a bundle of crimped cast-leaf tobacco wrapped in a filter paper (not shown) to form a plug. The cast-leaf tobacco includes additives, including glycerine as an aerosol-forming additive.

(16) The hollow acetate tube 30 is located immediately downstream of the aerosol-forming substrate 20 and is formed from cellulose acetate. One function of the tube 30 is to locate the aerosol-forming substrate 20 towards the distal end 13 of the rod 11 so that it can be contacted with a heating element. The tube 30 acts to prevent the aerosol-forming substrate 20 from being forced along the rod 11 towards the aerosol-cooling element 40 when a heating element is inserted into the aerosol-forming substrate 20. The tube 30 also acts as a spacer element to space the aerosol-cooling element 40 from the aerosol-forming substrate 20.

(17) The aerosol-cooling element 40 has a length of about 18 mm, an outer diameter of about 7.12 mm, and an inner diameter of about 6.9 mm. In one embodiment, the aerosol-cooling element 40 is formed from a sheet of polylactic acid having a thickness of 50 mm±2 mm. The sheet of polylactic acid has been crimped and gathered to define a plurality of channels that extend along the length of the aerosol-cooling element 40. The total surface area of the aerosol-cooling element is between 8000 mm.sup.2 and 9000 mm.sup.2, which is equivalent to approximately 500 mm.sup.2 per mm length of the aerosol-cooling element 40. The specific surface area of the aerosol-cooling element 40 is approximately 2.5 mm.sup.2/mg and it has a porosity of between 60% and 90% in the longitudinal direction. The polylactic acid is kept at a temperature of 160 degrees Celsius or less during use.

(18) Porosity is defined herein as a measure of unfilled space in a rod including an aerosol-cooling element consistent with the one discussed herein. For example, if a diameter of the rod 11 was 50% unfilled by the element 40, the porosity would be 50%. Likewise, a rod would have a porosity of 100% if the inner diameter was completely unfilled and a porosity of 0% if completely filled. The porosity may be calculated using known methods.

(19) An exemplary illustration of how porosity is calculated is provided here and illustrated in FIGS. 11A, 11B, and 11C. When the aerosol-cooling element 40 is formed from a sheet of material 1110 having a thickness (t) and a width (w) the cross-sectional area presented by an edge 1100 of the sheet material 1110 is given by the width multiplied by the thickness. In a specific embodiment of a sheet material having a thickness of 50 micrometers (±2 micrometers) and width of 230 millimetres, the cross-sectional area is approximately 1.15×10.sup.−5 m.sup.2 (this may be denoted the first area). An exemplary crimped material is illustrated in FIG. 11 with the thickness and width labelled. An exemplary rod 1200 is also illustrated having a diameter (d). The inner area 1210 of the rod is given by the formula (d/2).sup.2π. Assuming an inner diameter of the rod that will eventually enclose the material is 6.9 mm, the area of unfilled space may be calculated as approximately 3.74×10.sup.−5 m.sup.2 (this may be denoted the second area).

(20) The crimped or uncrimped material comprising the aerosol-cooling element 40 is then gathered or folded and confined within the inner diameter of the rod (FIG. 11B). The ratio of the first and second area based on the above examples is approximately 0.308. This ratio is multiplied by 100 and the quotient is subtracted from 100% to arrive at the porosity, which is approximately 69% for the specific figures given here. Clearly, the thickness and width of a sheet material may be varied. Likewise, the inner diameter of a rod may be varied.

(21) It will now be obvious to one of ordinary skill in the art that with a known thickness and width of a material, in addition to the inner diameter of the rod, the porosity can be calculated in the above manner. Accordingly, where a sheet of material has a known thickness and length, and is crimped and gathered along the length, the space filled by the material can be determined. The unfilled space may be calculated, for example, by taking the inner diameter of the rod. The porosity or unfilled space within the rod can then be calculated as a percentage of the total area of space within the rod from these calculations.

(22) The crimped and gathered sheet of polylactic acid is wrapped within a filter paper 41 to form the aerosol-cooling element 40.

(23) The mouthpiece filter 50 is a conventional mouthpiece filter formed from cellulose acetate, and having a length of about 45 millimetres.

(24) The four elements identified above are assembled by being tightly wrapped within a paper 60. The paper 60 in this specific embodiment is a conventional cigarette paper having standard properties. The interference between the paper 60 and each of the elements locates the elements and defines the rod 11 of the aerosol-generating article 10.

(25) Although the specific embodiment described above and illustrated in FIG. 1 has four elements assembled in a cigarette paper, it is clear than an aerosol-generating article may have additional elements or fewer elements.

(26) An aerosol-generating article as illustrated in FIG. 1 is designed to engage with an aerosol-generating device (not shown) in order to be consumed. Such an aerosol-generating device includes means for heating the aerosol-forming substrate 20 to a sufficient temperature to form an aerosol. Typically, the aerosol-generating device may comprise a heating element that surrounds the aerosol-generating article adjacent to the aerosol-forming substrate 20, or a heating element that is inserted into the aerosol-forming substrate 20.

(27) Once engaged with an aerosol-generating device, a user draws on the mouth-end 12 of the aerosol-generating article 10 and the aerosol-forming substrate 20 is heated to a temperature of about 375 degrees Celsius. At this temperature, volatile compounds are evolved from the aerosol-forming substrate 20. These compounds condense to form an aerosol, which is drawn through the rod 11 towards the user's mouth.

(28) The aerosol is drawn through the aerosol-cooling element 40. As the aerosol passes thorough the aerosol-cooling element 40, the temperature of the aerosol is reduced due to transfer of thermal energy to the aerosol-cooling element 40. Furthermore, water droplets condense out of the aerosol and adsorb to internal surfaces of the longitudinally extending channels defined through the aerosol-cooling element 40.

(29) When the aerosol enters the aerosol-cooling element 40, its temperature is about 60 degrees Celsius. Due to cooling within the aerosol-cooling element 40, the temperature of the aerosol as it exits the aerosol cooling element 40 is about 40 degrees Celsius. Furthermore, the water content of the aerosol is reduced. Depending on the type of material forming the aerosol-cooling element 40, the water content of the aerosol may be reduced from anywhere between 0 and 90%. For example, when element 40 is comprised of polylatic acid, the water content is not considerably reduced, i.e., the reduction will be approximately 0%. In contrast, when the starch based material, such as Mater-Bi, is used to form element 40, the reduction may be approximately 40%. It will now be apparent to one of ordinary skill in the art that through selection of the material comprising element 40, the water content in the aerosol may be chosen.

(30) Aerosol formed by heating a tobacco-based substrate will typically comprise phenolic compounds. Using an aerosol-cooling element consistent with the embodiments discussed herein may reduce levels of phenol and cresols by 90% to 95%.

(31) FIG. 2 illustrates a second embodiment of an aerosol-generating article. While the article of FIG. 1 is intended to be consumed in conjunction with an aerosol-generating device, the article of FIG. 2 comprises a combustible heat source 80 that may be ignited and transfer heat to the aerosol-forming substrate 20 to form an inhalable aerosol. The combustible heat source 80 is a charcoal element that is assembled in proximity to the aerosol-forming substrate at a distal end 13 of the rod 11. The article 10 of FIG. 2 is configured to allow air to flow into the rod 11 and circulate through the aerosol-forming substrate 20 before being inhaled by a user. Elements that are essentially the same as elements in FIG. 1 have been given the same numbering.

(32) The exemplary embodiments described above is not limiting. In view of the above-discussed exemplary embodiments, other embodiments consistent with the above exemplary embodiments will now be apparent to one of ordinary skill in the art.

(33) The following examples record experimental results obtained during tests carried out on specific embodiments of an aerosol-generating article comprising an aerosol-cooling element. Conditions for smoking and smoking machine specifications are set out in ISO Standard 3308 (ISO 3308:2000). The atmosphere for conditioning and testing is set out in ISO Standard 3402. Phenols were trapped using Cambridge filter pads. Quantitative measurement of phenolics, catechol, hydroquinone, phenol, o-, m- and p-cresol, was done by LC-fluorescence.

EXAMPLE 1

(34) This experiment was performed to assess the effect of incorporation of a crimped and gathered polylactic acid (PLA) aerosol-cooling element in an aerosol-generating article for use with an electrically heated aerosol-generating device. The experiment investigated the effect of the aerosol-cooling element on the puff per puff mainstream aerosol temperature. A comparative study with a reference aerosol-generating article without an aerosol-cooling element is provided.

Materials and Methods

(35) Aerosol-generating runs were performed under a Health Canada smoking regime: 15 puffs were taken, each of 55 mL in volume and 2 seconds puff duration, and having a 30 seconds puff interval. 5 blank puffs were taken before and after a run.

(36) Preheating time was 30 s. During the experiment, the laboratory conditions were (60±4)% relative humidity (RH) and a temperature of (22±1)° C.

(37) Article A is an aerosol-generating article having a PLA aerosol-cooling element. Article B is a reference aerosol-generating article without an aerosol-cooling element.

(38) The aerosol-cooling element is made of 30 μm thick sheet of EarthFirst®PLA Blown Clear Packaging Film made from renewable plant resources and traded under the trade name Ingeo™ (Sidaplax, Belgium). For mainstream aerosol temperature measurement, 5 replicates per sample were measured.

Results

(39) The average mainstream aerosol temperature per puff taken from Article A and Article B are shown in FIG. 3. The intra-puff mainstream temperature profile of puff number 1 of Article A and Article B are shown in FIG. 4.

EXAMPLE 2

(40) This experiment was performed to assess the effect of incorporation of a crimped and gathered starch based copolymer aerosol-cooling element in an aerosol-generating article for use with an electrically heated aerosol-generating device. The experiment investigated the effect of the aerosol-cooling element on the puff per puff mainstream aerosol temperature. A comparative study with a reference aerosol-generating article without an aerosol-cooling element is provided.

Materials and Methods

(41) Aerosol-generating runs were performed under a Health Canada smoking regime: 15 puffs were taken, each of 55 mL in volume and 2 seconds puff duration, and having a 30 seconds puff interval. 5 blank puffs were taken before and after a run.

(42) Preheating time was 30 s. During the experiment, the laboratory conditions were (60±4)% relative humidity (RH) and a temperature of (22±1)° C.

(43) Article C is an aerosol-generating article having a starch based copolymer aerosol-cooling element. Article D is a reference aerosol-generating article without an aerosol-cooling element.

(44) The aerosol-cooling element is 25 mm in length and made of a starch based copolyester compound. For mainstream aerosol temperature measurement, 5 replicates per sample were measured.

Results

(45) The average mainstream aerosol temperature per puff and its standard deviation for both systems (i.e. Articles C and D) are shown in FIG. 5.

(46) The puff per puff mainstream aerosol temperature for the reference system Article D decreases in a quasi linear manner. The highest temperature was reached during puffs 1 and 2 (about 57-58° C.) while the lowest were measured at the end of the smoking run during puffs 14 and 15, and are below 45° C. The use of a starch based copolyester compound crimped and gathered aerosol-cooling element significantly reduces the mainstream aerosol temperature. The average aerosol temperature reduction shown in this specific example is about 18° C., with a maximum reduction of 23° C. during puff number 1 and a minimum reduction of 14° C. during puff number 3.

EXAMPLE 3

(47) In this example, the effect of a polylactic acid aerosol-cooling element on puff per puff mainstream aerosol nicotine and glycerine levels was investigated.

Materials and Methods

(48) Puff per puff nicotine and glycerine deliveries were measured by gas chromatography/time-of-flight mass spectrometry (GC/MS-TOF). Runs were performed as described in example 1. Articles A and B are articles as described in Example 1.

Results

(49) Nicotine and glycerine puff per puff release profiles of Article A and Article B are shown in FIGS. 6 and 7.

EXAMPLE 4

(50) In this example, the effect of a starch based copolyester aerosol-cooling element on the puff per puff mainstream aerosol nicotine and glycerine levels was investigated.

Materials and Methods

(51) Puff per puff nicotine and glycerine deliveries are measured by GC/MS-TOF. Runs were performed as described in example 2. Articles C and D are articles as described in Example 1. Articles A and B are articles as described in Example 1.

(52) Puff per puff nicotine and glycerine deliveries are shown in FIGS. 8 and 9. The total nicotine yields with a starch based copolyester compound crimped filter was 0.83 mg/cigarette (σ=0.11 mg) and 1.04 mg/cigarette (σ=0.16 mg). The reduction in nicotine yields is clearly visible in FIG. 8 and occurs mainly between puffs 3 and 8. The use of a starch based copolyester compound aerosol-cooling element reduced the variability in puff per puff nicotine yields (cv=38% with crimped filter, cv=52% without filter). Maximum nicotine yield per single puff is 80 μg with the aerosol-cooling element and up to 120 μg without.

EXAMPLE 5

(53) In this example, the effect of a polylactic acid aerosol-cooling element on the total mainstream aerosol phenol yield was investigated. In addition, the effect of a polylactic acid aerosol-cooling element on mainstream aerosol phenol yields in comparison with international reference cigarette 3R4F, on nicotine base is provided.

Materials and Methods

(54) Analysis of phenols was performed. The number of replicates per prototype was 4. Laboratory conditions and testing regime were as described in example 1. Articles A and B are as described in example 1. Mainstream aerosol phenols yields for the systems with and without the aerosol-cooling element are presented in Table 1. For comparison purposes, mainstream smoke values for the Kentucky reference cigarette 3R4F are also given in Table 1. Kentucky reference cigarette 3R4F is a commercially available reference cigarette available, for example, from the College of Agriculture, Tobacco Research & Development center at the University of Kentucky.

(55) TABLE-US-00001 TABLE 1 Mainstream phenols yields for Article B, Article A, and 3R4F reference cigarette. Yields are given in μg/cigarette. Phenol o-Cresol m-Cresol p-Cresol Catechol Hydroquinone avg Sd avg Sd Avg sd avg sd avg Sd avg sd Article B 7.9 0.5 0.52 0.02 0.27 0.03 0.60 0.03 7.4 0.8 5.0 0.6 Article A <0.6 — 0.18 0.01 <0.15 — <0.29 — 8.6 0.8 5.0 0.9 3R4F 11.7 0.6 3.9 0.2 3.1 0.1 7.9 0.4 83.9 2.1 78.1 2.4

(56) The most dramatic effect of the addition of a PLA aerosol-cooling element in this specific example is observed for phenol, where the reduction in phenol is greater than 92% versus the reference system without an aerosol cooling element, and 95% versus the 3R4F reference cigarette (expressed on a per mg of nicotine basis). The phenols yields (in nicotine basis) reduction percentages are given in Table 2 expressed per mg of nicotine.

(57) TABLE-US-00002 TABLE 2 Phenols yields reduction (in nicotine basis) expressed in %. Phenol o-Cresol m-Cresol p-Cresol Catechol Hydroquinone % reduction % reduction % reduction % reduction % reduction % reduction Article A vs. Article B >91 60 >36 >45 +32 +13 Article A vs. 3R4F >89 90 >90 >92 79 86

(58) The variation of the mainstream smoke phenol yields versus 3R4F (in nicotine basis) as a function of the mainstream smoke deliveries is given in FIG. 10.

EXAMPLE 6

(59) In this example, the effect of a polylactic acid aerosol-cooling element on the puff per puff mainstream smoke phenol yield was investigated.

Materials and Methods

(60) Analysis of phenols was performed. Number of replicates per prototype was 4. Conditions were as described in example 1. Articles A and B are as described in example 1.

Results

(61) Phenol and nicotine puff per puff profiles for Articles A and B are given in FIGS. 8 and 9. For the system of Article B, mainstream aerosol phenol was detected as of puff number 3 and reached a maximum as of puff number 7. The effect of the PLA aerosol-cooling element on the puff per puff phenol deliveries is clearly visible, since phenol deliveries are below the limit of detection (LOD). A reduction in the total yield of nicotine and a flattening of the puff per puff nicotine release profile was observed in FIG. 9.