EP0337504B1

EP0337504B1 - Aerosol generating means for a smoking article and smoking article with such means

Info

Publication number: EP0337504B1
Application number: EP89110762A
Authority: EP
Inventors: Chandra Kumar Banerjee; Ernest Gilbert Farrier; James Luther Harris; Alan Benson Norman; James Lee Resce; John Hughes Reynolds, Iv; Henry Thomas Ridings; Andrew Jackson Sensabaugh, Jr.; Michael David Shannon; Gary Roger Shelar
Original assignee: RJ Reynolds Tobacco Co
Current assignee: RJ Reynolds Tobacco Co
Priority date: 1985-08-26
Filing date: 1986-07-14
Publication date: 1993-09-22
Anticipated expiration: 2006-07-14
Also published as: FI863428A0; DK166707B1; EP0340808A3; EG17790A; MY101072A; DK174428B1; DK17391D0; DE3650177D1; DK404086A; DK404086D0; NO166566B; EP0336457A2; EP0336457A3; EP0337504A3; ZW13686A1; IL79124A; EP0337505A2; IL79124A0; MA20757A1; JPH03114471A

Abstract

A member is provided for conducting heat from a combustible fuel element to an 'aerosol' generator which includes aerosol-forming material. The conducting member is spaced from the lighting end of the fuel element by at least 5 mm., and can circumscribe both the fuel element and generator, at least partially. Alternatively, the conductor contacts the fuel element along less than approx. half its length, e.g. it is embedded within it. Pref. the fuel element has a length of less than approx. 30 mm and has a density of about 0.5 g/cc.

Description

The present invention relates to an aerosol generating means for use with a smoking article and a smoking article which comprises a combustible fuel element and such an aerosol generating means according to the preamble of claims 1 and 17.
Many smoking articles of this type have been proposed through the years, especially over the last 20 to 30 years, but none of these products has ever realized any commercial success.
EP-A-0 117 355 (Hearn et al.) describes a proposed cigarette smoking article having a carbon heat source with an axial passageway and a separate flavor generator. The heat source (page 2, line 23 to page 7, line 14) is formed by pyrolyzing a preformed, tube-shaped ligno-cellulosic material of e.g. 90 mm or 65 mm length (see Comparative Example 1 and Example 4, respectively) under specified conditions, followed by at least one additional specified process step. The purported flavor generator (page 8, lines 8-27) comprises a substrate material, which may be tobacco, alumina, etc., adjacent the mouth end, which is impregnated with or inherently contains at least one thermally releasable flavorant. The flavor generator also may comprise a flavored, foamed core inside the heat source. A conventional filter may be placed after the flavor generator. The purported formation of an aerosol during use is described from page 8, line 28 to page 9, line 8. The heat source, the flavor generator and the filter are wrapped in cigarette paper.
Despite decades of interest and effort, there is still no smoking article on the market which provides the benefits and advantages associated with conventional cigarette smoking, without delivering considerable quantities of incomplete combustion and pyrolysis products generated by a conventional cigarette.
It is the object of the present invention to provide an aerosol generating means for a smoking article of the type having a fuel element and a separate aerosol generating means which has an improved shelf life time.
According to subject invention this object is achieved by an aerosol generating means for use with a smoking article, comprising a substrate including alumina, said substrate bearing an aerosol forming substance composed of (molecules comprising) at least carbon, hydrogen, and oxygen, wherein said substrate includes alumina sintered at temperatures greater than about 1000° C.
In the inventive aerosol generating means the aerosol forming substance is more effectively retained in the substrate prior to smoking.
In order to resemble the smoke of a regular cigarette, in a preferred embodiment of the inventive aerosol generating means said substrate bears a volatile tobacco flavor agent.
In accordance with subject invention it is recommended to wash and dry the sintered alumina prior to use in order to avoid any undesired taste.
Preferably, the substrate is of a type which withstands temperatures up to 400° to 600° C.
In preferred embodiments the aerosol forming substance is in solid and/or liquid form.
In order to obtain as much aerosol as possible it is recommended to use an aerosol forming substance the boiling point of which is in a temperature range up to 500° C.
Preferred aerosol forming substances by which an aerosol resembling the smoke of a regular smoking article can easily be produced include polyhydric alcohols, most preferably glycerin and/or propylene glycol and/or triethylene glycol.
In order to further improve the taste of the aerosol obtained by an inventive aerosol generating means it is recommended that said tobacco flavor agent comprises a tobacco extract.
Preferred embodiments of the inventive aerosol generating means contain an aerosol forming substance comprising a tobacco flavor modifier. In order to further smoothen the taste of the aerosol and/or to obtain an aerosol with a caramel taste it is recommended to use a tobacco flavor modifier which comprises levulinic acid. In addition or as an alternative the tobacco flavor agent may comprise menthol.
In order to obtain from a smoking article incorporating the inventive aerosol generating means about the same number of puffs as from a conventional cigarette it is recommended to use from about 20 mg to about 120 mg, preferably from about 35 mg to about 85 mg, and most preferably from about 45 mg to about 65 mg of liquid aerosol forming substance.
The present invention is further directed to a smoking article comprising a fuel element and a physically separate aerosol generating means having one or several of the features specified above.
Preferably, such a smoking article is designed such that above about 2 weight percent, preferably above about 15 weight percent, and most preferably above about 20 weight percent of the aerosol forming substance carried on the substrate are delivered to the user as WTPM.
A preferred embodiment of the invention comprises a smoking article, preferably in cigarette form, which utilizes a small, high density combustible fuel element in conjunction with a physically separate aerosol generating means which includes one or more aerosol forming materials. Preferably, the aerosol generating means is in a conductive heat exchange relationship with the fuel element and/or at least a portion of the fuel element is circumscribed by a resilient insulating jacket to reduce radial heat loss. Upon lighting, the fuel element generates heat which is used to volatilize the aerosol forming materials in the aerosol generating means. These volatile materials are then drawn toward the mouth end, especially during puffing, and into the user's mouth, akin to the smoke of a conventional cigarette.
Smoking articles of the invention are capable of producing substantial quantities of aerosol, both initially and over the useful life of the product, and are capable of providing the user with the sensations and benefits of cigarette smoking. The aerosol produced by the aerosol generating means is produced without significant thermal degradation and is advantageously delivered to the user with substantially reduced amounts of pyrolysis and incomplete combustion products than are normally delivered by a conventional cigarette.
The smoking article of the present invention also may include a charge or plug of tobacco which may be used to add a tobacco flavor to the aerosol. A tobacco charge may be mixed with the substrate for the aerosol forming material. Other substances, such as flavoring agents, also may be incorporated into the article to flavor or otherwise modify the aerosol delivered to the user.
As used herein, and only for the purposes of this application, "aerosol" is defined to include vapors, gases, particles, and the like, both visible and invisible, and especially those components perceived by the user to be "smoke-like," generated by action of the heat from the burning fuel element upon substances contained within the aerosol generating means, or elsewhere in the article. As so defined, the term "aerosol" also includes volatile flavoring agents and/or pharmacologically or physiologically active agents irrespective of whether they produce a visible aerosol.
It is proposed to have the aerosol forming material enclosed within a heat conductive container.
The present invention is described in greater detail in the accompanying drawings and in the detailed description of the invention which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1 through 9 are longitudinal sectional views of various embodiments of the invention;
Figure 1A is a sectional view of the embodiment of Figure 1, taken along lines 1A-1A in Figure 1;
Figure 2A is a sectional view of the embodiment of Figure 2, taken along lines 2A-2A in Figure 2;
Figure 6A is a sectional view of the embodiment of Figure 6, taken along lines 6A-6A in Figure 6;
Figures 7A, 7B, 7C, and 9A are end views showing various fuel element passageway configurations suitable for use in embodiments of the invention;
Figure 8A is a sectional view of the embodiment of Figure 8, taken along lines 8-8 in Figure 8;
Figure 8B is an enlarged end view of the metallic container employed in the embodiment of Figure 8; and
Figure 9B is a longitudinal sectional view of a preferred fuel element passageway configuration suitable for use in embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment of the invention illustrated in Figure 1, which preferably has the overall dimensions of a conventional cigarette, includes a short, about 20 mm long, combustible fuel element 10, an abutting aerosol generating means 12, and a foil lined paper tube 14, which forms the mouthend 15 of the article. In this embodiment, fuel element 10 is extruded or molded from a mixture containing comminuted or reconstituted tobacco and/or a tobacco substitute and a minor amount of combustible carbon, and is provided with five longitudinally extending holes 16. See Figure 1A. The lighting end of fuel element 10 may be tapered or reduced in diameter to improve ease of lighting.
Aerosol generating means 12 includes a porous mass 13 which is provided with one or more passages 17 and is impregnated with one or more aerosol forming materials, such as triethylene glycol, propylene glycol, glycerin, or mixtures thereof.
The foil lined paper tube 14, which forms the mouthend piece of the article, surrounds aerosol generating means 12 and the rear, nonlighting end of fuel element 10 so that the foil lined tube is spaced about 15 mm from the lighting end of the fuel element. The tube 14 also forms an aerosol delivery passage 18 between the aerosol generating means 12 and mouth end 15 of the article. The presence of foil lined tube 14, which couples the nonlighting end of fuel 10 to aerosol generator 12, increases heat transfer to the aerosol generator. The foil also helps to extinguish the fire cone. When only a small amount of the unburned fuel remains, heat loss through the foil acts as a heat sink which helps to extinguish the fire cone. The foil used in this article is typically an aluminum foil of 0.35 mils (0.0089 mm) in thickness, but the thickness and/or the type of conductor employed may be varied to achieve virtually any desired degree of heat transfer.
The article illustrated in Figure 1 also includes an optional mass or plug of tobacco 20 to contribute flavor to the aerosol. This tobacco charge 20 may be placed at the mouth end of carbon mass 13, as shown in Figure 1, or it may be placed in passage 18 at a location spaced from aerosol generator 12. For appearance sake, the article may include an optional low efficiency cellulose acetate filler 22, positioned at or near the mouth end 15.
The embodiment of the invention illustrated in Figure 2, includes a short combustible fuel element 24, about 20 mm long, connected to aerosol generating means 12 by a heat conductive rod 26 and by a foil lined paper tube 14, which also leads to the mouth end 15 of the article. Aerosol generating means 12 includes a thermally stable substrate 28, such as a plug of porous carbon, which is impregnated with one or more aerosol forming materials. This embodiment includes a void space 30 between the fuel element 24 and the substrate 28. The portion of the foil lined tube 14 surrounding this void space includes a plurality of peripheral holes 32 which permit sufficient air to enter the void space to provide appropriate pressure drop.
As shown in Figures 2 and 2A, the heat conducting means includes the conductive rod 26 and the foil lined tube 14, both of which are spaced from the lighting end of the fuel element. The rod 26 is spaced about 5 mm from the lighting end; the tube about 15 mm. The rod 26 is preferably formed of aluminum and has at least one, preferably from 2 to 5, peripheral grooves 34 therein, to allow air passage through the substrate. The article of Figure 2 has the advantage that the air introduced into void space 30 contains less oxidation products because it is not drawn through the burning fuel.
The embodiment illustrated in Figure 3 includes fuel element 10, about 10 mm long, with a single axial hole 16. Again, the lighting end of the fuel element may be tapered or reduced in diameter to improve ease of lighting. The substrate 38 of the aerosol generator is a granular, thermally stable alumina impregnated with an aerosol forming material. A mass of tobacco 20 is located immediately behind the substrate. This article is provided with a cellulose acetate tube 40, in place of the foil lined tube of previous embodiments. This tube 40 includes an annular sect on 42 of resilient cellulose acetate tow surrounding an optional plastic tube 44 of polypropylene, Nomex, Mylar, or the like. At the mouth end 15 of this element there is a low efficiency cellulose acetate filter plug 45.
The entire length of the article may be wrapped in cigarette-type paper 46. A cork or white ink coating 48 may be used on the mouth end to simulate tipping. A foil strip 50 is located on the inside of the paper, toward the fuel end of the article. This strip preferably overlaps the rear 2 to 3 mm of the fuel element and extends to the mouth end of the tobacco charge 20. It may be integral with the paper or it may be a separate piece applied before the paper overwrap.
The embodiment of Figure 4 is similar to that of Figure 3. In this embodiment, the fuel element 10 is about 15 mm long and the aerosol generating means 12 is formed by an aluminum capsule 52 which is filled with a granular substrate or, as shown in the drawing, a mixture of a granular substrate 54 and tobacco 56. The capsule 52 is crimped at its ends 58, 60 to enclose the material and to inhibit migration of the aerosol former. The crimped end 58, at the fuel end, preferably abuts the rear end of the fuel element to provide for conductive heat transfer.
A void space 62 formed by end 58 also helps to inhibit migration of the aerosol former to the fuel. Longitudinal passageways 59 and 61 are provided to permit the passage of air and the aerosol forming material. Capsule 52 and fuel element 10 may be united by a conventional cigarette paper 47, as illustrated in the drawing, by a perforated ceramic paper, or a metallic strip or tube. If cigarette paper is used, a strip 64 near the rear end of the fuel should be printed or treated with sodium silicate or other known materials which cause the paper to extinguish. If a metal foil is used, it preferably should be spaced about 8 to 12 mm from the lighting end of the fuel. The entire length of the article may be overwrapped with conventional cigarette paper 46.
The embodiment shown in Figure 5 illustrates the use of a substrate 66 impregnated with one or more aerosol forming materials and which is embedded within a large cavity 68 in fuel element 10. In this type of embodiment, the substrate 66 usually is a relatively rigid, porous material. The entire length of the article may be wrapped with conventional cigarette paper 46. This embodiment may also include a foil strip 70 to couple fuel element 10 to the cellulose acetate tube 40 and to help extinguish the fuel. This strip is spaced about 5 to 10 mm from the lighting end.
The embodiments shown in Figures 6 through 8 include a resilient insulating jacket which encircles or circumscribes the fuel element to insulate and help concentrate the heat in the fuel element. These embodiments also help to reduce any fire causing potential of the burning fire cone and, in some cases, help simulate the feel of a conventional cigarette.
In the embodiment of Figure 6, the fuel element 10 is provided with a plurality of holes 16 and is circumscribed by a resilient jacket 72 about 0.5 mm thick, as shown in Figure 6A. This jacket is formed of insulating fibers, such as ceramic (e.g., glass) fibers or nonburning carbon or graphite fibers. The aerosol generating means 12 comprises a porous mass 13 having a single, axial hole 17.
In the embodiment of Figure 7, the resilient, glass fiber insulating jacket 72 surrounds the periphery of both fuel element 10 and aerosol generating means 12 and is preferably a low temperature material which fuses during use. This jacket 72 is overwrapped with a non-porous paper 73, such as P 878-5 obtained from Kimberly-Clark. In this embodiment, the fuel element is about 15 to 20 mm long and is preferably provided with three or more holes 16 to increase air flow through the fuel. Three suitable passageway arrangements are illustrated in Figures 7A, 7B, and 7C.
In this embodiment, the aerosol generating means 12 comprises a metallic container 74 which encloses a granular substrate 38 and densified tobacco 76, and at least the substrate includes an aerosol forming material. As illustrated, the open end 75 of container 74 overlaps the rear 3 to 5 mm portion of fuel element 10. Alternatively, the open end 75 may abut the rear end of fuel element 10. The opposite end of container 74 is crimped to form wall 78, which is provided with a plurality of passages 80 to permit passage of gases, tobacco flavors, and/or the aerosol forming material into aerosol delivery passage 18.
Plastic tube 44 abuts or preferably overlaps walled end 78 of metallic container 74 and is surrounded by a section of resilient, high density cellulose acetate tow 42. A layer of glue 82, or other material, may be applied to the fuel end of tow 42 to seal the tow and block air flow therethrough. A low efficiency filter plug 45 is provided at the mouth end of the article, and tow 42 and filter plug 45 are preferably overwrapped with a conventional plug wrap paper 85. Another layer of cigarette paper 86 may be used to join the rear portion of the insulating jacket 72 and the tow/filter section.
In a modified version of the embodiment of Figure 7, the insulating jacket may also be used in lieu of the cellulose acetate tow 42, so that the jacket extends from the lighting end to the filter plug 45. In embodiments of this type, a layer of glue is preferably applied to the annular section of the filter plug which abuts the end of the insulating jacket, or a short annular section of tow is placed between the insulating jacket and the filter piece, with glue applied at either end.
Figure 8 illustrates an embodiment in which a 10 to 15 mm long fuel element 10 is overwrapped with an insulating jacket 72 of glass fibers and the aerosol generating means is circumscribed by a jacket of tobacco 88. The glass fibers used on this embodiment preferably have a softening temperature below about 650^°C, such as experimental fibers 6432 and 6437 obtained from Owens-Corning, Toledo, Ohio, so that they will fuse during use. The glass fiber and tobacco jackets are each wrapped with a plug wrap 85, such as Ecusta 646, and are joined by an overwrap of cigarette paper 89, such as 780-63-5 or P 878-16-2, obtained from Kimberly-Clark. In this embodiment, the metallic capsule 90 overlaps the rear 3 to 4 mm of the fuel element so that it is spaced about 6 to 12 mm from the lighting end, and the rear portion of the capsule 90 is crimped into a lobe shape, as shown in Figure 8B. A passage 91 is provided at the mouth end of the capsule, in the center of the capsule. Four additional passages 92 are provided at the transition points between the crimped and uncrimped portion of the capsule. Alternatively, the rear portion of the capsule may have a rectangular of square cross section in lieu of the lobes, or a simple tubular capsule with a crimped mouth end may be employed, with or without peripheral passages 92.
At the mouth end of tobacco jacket 88 is a mouthend piece 40 including an annular section of cellulose acetate tow 42, a plastic tube 44, a low efficiency filter piece 45, and layers of cigarette paper 85 and 89. The mouth end piece 40 is joined to the jacketed fuel/capsule end by an overwrapping layer of tipping paper 86. As illustrated, the capsule end of plastic tube 44 is spaced from the capsule 90. Thus, the hot vapors flowing through passages 92 pass through tobacco jacket 88, where volatile components in the tobacco are vaporized or extracted, and then into passage 18 where the tobacco jacket abuts the cellulose acetate tow 42.
In embodiments of this type having low density fuel insulating jackets 72, some air and gases pass through jacket 72 and into tobacco jacket 88. Thus, the peripheral passage 92 in the capsule may not be needed to extract tobacco flavor from the tobacco jacket 88.
In the embodiment of Figure 9, the jacket 94 comprises tobacco or an admixture of tobacco and insulating fibers, such as glass fibers. As shown, the tobacco jacket 94 extends just beyond the mouth end of metallic container 96. Alternatively, it may extend over the entire length of the article, up to the mouth end filter piece. In embodiments of this type, container 96 is preferably provided with one or more longitudinal slots 99 on its periphery (preferably two slots 180^o apart) so that vapors from the aerosol generator pass through the annular section of tobacco which surrounds the aerosol generator to extract tobacco flavors before entering passage 18.
As illustrated, the tobacco at the fuel element end of jacket 94 is compressed. This aids in reducing air flow through the tobacco, thereby reducing the burn potential thereof. In addition, the container 96 aids in extinguishing the tobacco by acting as a heat sink. This heat sink effect helps quench any burning of the tobacco surrounding the capsule, and it also helps to evenly distribute heat to the tobacco around the aerosol generating means, thereby aiding in the release of tobacco flavor components. In addition, it may be desirable to treat the portion of the cigarette paper overwrap 85, 89 near the rear end of the fuel with a material, such as sodium silicate, to help extinguish the tobacco, so that it will not burn significantly beyond the exposed portion of the fuel element. Alternatively, the tobacco itself may be treated with a burn modifier to prevent burning of the tobacco which surrounds the aerosol generator.
Upon lighting any of the aforesaid embodiments, the fuel element burns, generating the heat used to volatilize the aerosol forming material or materials present in the aerosol generating means. These volatile materials are then drawn toward the mouthend, especially during puffing, and into the user's mouth, akin to the smoke of a conventional cigarette.
Because the fuel element is relatively short, the hot, burning fire cone is always close to the aerosol generating body, which maximizes heat transfer to the aerosol generating means and any optional tobacco charges, and the resultant production of aerosol and optional tobacco flavor, especially when the preferred heat conducting member is used. Because the fuel element is short, there is never a long section of nonburning fuel to act as a heat sink, as was common in previous thermal aerosol articles. The small fuel source also tends to minimize the amount of incomplete combustion or pyrolysis products, especially in embodiments which contain carbon and/or multiple passageways.
Because the aerosol forming material is physically separate from the fuel element, it is exposed to substantially lower temperatures than are present in the burning fire cone. This minimizes the possibility of thermal degradation of the aerosol former and attendant off taste. This also results in aerosol production during puffing, but minimal aerosol production from the aerosol generating means during smolder.
In the preferred embodiments of the invention, the short fuel element, the recessed heat conducting member, the insulating member, and/or the passages in the fuel cooperate with the aerosol generator to provide a system which is capable of producing substantial quantities of aerosol and optional tobacco flavor, on virtually every puff. The close proximity of the fire cone to the aerosol generator after a few puffs, together with the conducting member, the insulating member, and/or the multiple passageways in the fuel element, results in high heat delivery both during puffing and during the relatively long period of smolder between puffs.
While not wishing to be bound by theory, it is believed that the aerosol generating means is maintained at a relatively high temperature between puffs, and that the additional heat delivered during puffs, which is significantly increased by the preferred passageways in the fuel element, is primarily utilized to vaporize the aerosol forming material. This increased heat transfer makes more efficient use of the available fuel energy, reduces the amount of fuel needed, and helps deliver early aerosol.
In general, the combustible fuel elements which may be employed in practicing the invention are less than about 30 mm long. Preferably the fuel element is about 20 mm or less, more preferably about 15 mm or less in length. Advantageously, the diameter of the fuel element is about 8 mm or less, preferably between about 3 and 7 mm, and more preferably between about 4 to 6 mm. The density of the fuel elements which nay be employed herein range from about 0.5 g/cc to about 1.5 g/cc as measured, e.g., by mercury displacement. Preferably, the density is greater than 0.7 g/cc., more preferably greater than 0.8 g/cc. In most cases, a high density material is desired because it helps to ensure that the fuel element will burn long enough to simulate the burning time of a conventional cigarette and that it will provide sufficient energy to generate the required amount of aerosol.
The most preferred fuel elements useful in practicing this invention are carbonaceous fuel elements (i.e., fuel elements primarily comprising carbon). Carbonaceous fuel elements are particularly advantageous because they produce minimal pyrolysis and incomplete combustion products, produce little or no visible sidestream smoke, and minimal ash, and have high heat capacity. In especially preferred embodiments, the aerosol delivered to the user has no significant mutagenic activity as measured by the Ames test. See Ames et al., Mut. Res., 31:347-364 (1975); Nagas et al., Mut. Res., 42:335 (1977).
The aerosol generating means used in practicing the invention is physically separate from the fuel element. By physically separate it is meant that the substrate, container, or chamber which contains the aerosol forming materials is not mixed with, or a part of, the burning fuel element. As noted previously, this arrangement helps reduce or eliminate thermal degradation of the aerosol forming material and the presence of sidestream smoke. While not a part of the fuel, the aerosol generating means is preferably in a conductive heat exchange relationship with the fuel element, and preferably abuts or is adjacent to the fuel element. More preferably, the conductive heat exchange relationship is achieved by a heat conducting member, such as a metal tube or foil, which is preferably recessed or spaced from the lighting end of the fuel.
The aerosol generating means includes one or more thermally stable materials which carry one or more aerosol forming materials. As used herein, a thermally stable material is one capable of withstanding the high temperatures, e.g., 400°C-600°C, which exist near the fuel without decomposition or burning. While not preferred, other aerosol generating means, such as heat rupturable microcapsules, or solid aerosol forming substances, are within the scope of the invention, provided they are capable of releasing sufficient aerosol forming vapors to satisfactorily resemble tobacco smoke.
Thermally stable materials which may be used as a substrate or carrier for the aerosol forming materials are well known to those skilled in the art. Useful substrates should be porous and must be capable of retaining an aerosol forming material when not in use and capable of releasing a potential aerosol forming vapor upon heating by the fuel element. Substrates, especially particulates, may be placed within a container, preferably formed from a conductive material.
Suitable materials include alumina, sintered at temperatures greater than about 1000°C. A preferred alumina substrate is SMR-14-1896, available from the Davidson Chemical Division of W.R. Grace & Co., which is sintered at elevated temperatures greater than about 1000°C, washed, and dried prior to use.
The aerosol generating means used in the invention is advantageously spaced no more than about 40 mm, preferably no more than 30 mm, most preferably no more than 20 mm from the lighting end of the fuel element. The aerosol generator may vary in length from about 2 mm to about 60 mm, preferably from about 5 mm to 40 mm, and most preferably from about 20 mm to 35 mm. The diameter of the aerosol generating means may vary from about 2 mm to about 8 mm, preferably from about 3 to 6 mm. If a non-particulate substrate is used, it may be provided with one or more holes, to increase the surface area of the substrate, and to increase air flow and heat transfer.
The aerosol forming material or materials used in the invention must be capable of forming an aerosol at the temperature present in the aerosol generating means when heated by the burning fuel element. Such materials preferably will be composed of carbon, hydrogen and oxygen, but they may include other materials. The aerosol forming materials can be in solid, semisolid, or liquid form. The boiling point of the material and/or the mixture of materials can range up to about 500^oC. Substances having these characteristics include polyhydric alcohols, such as glycerin and propylene glycol, as well as aliphatic esters of mono-, di-, or poly-carboxylic acids, such as methyl stearate, dodecandioate, dimethyl tetradodecandioate, and others.
The preferred aerosol forming materials are polyhydric alcohols, or mixtures of polyhydric alcohols. Especially preferred aerosol formers are glycerin, propylene glycol, triethylene glycol, or mixtures thereof.
The aerosol forming material may be dispersed on or within the aerosol generating means in a concentration sufficient to permeate or coat the substrate, carrier, or container. For example, the aerosol forming substance may be applied full strength or in a dilute solution by dipping, spraying, vapor deposition, or similar techniques. Solid aerosol forming components may be admixed with the substrate and distributed evenly throughout prior to formation.
While the loading of the aerosol forming material will vary from carrier to carrier and from aerosol forming material to aerosol forming material, the amount of liquid aerosol forming materials may generally vary from about 20 mg to about 120 mg, preferably from about 35 mg to about 85 mg, and most preferably from about 45 mg to about 65 mg. As much as possible of the aerosol former carried on the aerosol generating means should be delivered to the user as WTPM. Preferably, above about 2 weight percent, more preferably above about 15 weight percent, and most preferably above about 20 weight percent of the aerosol former carried on the aerosol generating means is delivered to the user as WTPM.
The aerosol generating means also may include one or more volatile flavoring agents, such as menthol, vanillin, artificial coffee, tobacco extracts, nicotine, caffeine, liquors, and other agents which impart flavor to the aerosol. It also may include any other desirable volatile solid or liquid materials. Alternatively, these optional agents may be placed between the aerosol generating means and the mouthend, such as in a separate substrate or chamber in the passage which leads from the aerosol generating means to the mouthend, or in the optional tobacco charge. If desired, these volatile agents may be used in lieu of part, or all, of the aerosol forming material, so that the article delivery a nonaerosol flavor or other material to the user.
One particularly preferred aerosol generating means comprises the aforesaid alumina substrate containing spray dried tobacco extract, tobacco flavor modifiers, such as levulinic acid, one or more flavoring agents, and an aerosol forming material, such as glycerin. This substrate may be mixed with densified tobacco particles, such as those produced on a "Marumerizer", which particles also may be impregnated with an aerosol forming material.
Articles of the type disclosed herein may be used, or may be modified for use, as drug delivery articles, for delivery of volatile pharmacologically or physiologically active materials such as ephedrine, metaproterenol, terbutaline or the like.
Preferred embodiments of the invention are capable of delivering at least 0.6 mg of aerosol, measured as wet total particulate matter (WTPM), in the first 3 puffs, when smoked under FTC smoking conditions. (FTC smoking conditions consist of two seconds of puffing (35 ml total volume) separated by 58 seconds of smolder.) More preferred embodiments of the invention are capable of delivering 1.5 mg or more of aerosol in the first 3 puffs. Most preferably, embodiments of the invention are capable of delivering 3 mg or more of aerosol in the first 3 puffs when smoked under FTC smoking conditions. Moreover preferred embodiments of the invention deliver an average of at least about 0.8 mg of wet total particulate matter per puff for at east about 6 puffs, preferably for at least about 10 puffs, under FTC smoking conditions.

Claims

An aerosol generating means (12; 90; 96) for use with a smoking article, comprising a substrate (13; 38; 54; 66) including alumina, said substrate bearing an aerosol forming substance composed of at least carbon, hydrogen, and oxygen, characterized in that said substrate (13; 38; 54; 66) includes alumina sintered at temperatures greater than about 1000° C.
An aerosol generating means according to claim 1, wherein said substrate (13; 38; 54; 66) bears a volatile tobacco flavor agent.
An aerosol generating means according to claim 1 or 2, wherein the sintered alumina is washed and dried prior to use.
An aerosol generating means according to one of the preceding claims, wherein said substrate withstands temperatures up to 400° to 600° C.
An aerosol generating means according to one of the preceding claims, wherein said aerosol forming substance is in solid form.
An aerosol generating means according to one of claims 1 to 4, wherein said aerosol forming substance is in a liquid form.
An aerosol generating means according to one of the preceding claims, wherein the boiling point of said substance is in a temperature range up to 500° C.
An aerosol generating means according to one of the preceding claims, wherein said substance includes polyhydric alcohols.
An aerosol generating means according to claim 8, wherein said polyhydric alcohol comprises glycerin and/or propylene glycol and/or triethylene glycol.
An aerosol generating means according to one of claims 2 to 9, wherein said tobacco flavor agent comprises a tobacco extract.
An aerosol generating means according to one of the preceding claims, wherein said aerosol forming substance comprises a tobacco flavor modifier.
An aerosol generating means according to claim 11, wherein the tobacco flavor modifier comprises levulinic acid.
An aerosol generating means according to one of claims 2 to 12, wherein said tobacco flavor agent comprises menthol.
An aerosol generating means according to one of claims 6 to 13, wherein the amount of liquid aerosol forming substance varies from about 20 mg to about 120 mg.
An aerosol generating means according to claim 14, wherein the amount of liquid aerosol forming substance varies from about 35 mg to about 85 mg.
An aerosol generating means according to claim 15, wherein the amount of liquid aerosol forming substance varies from about 45 mg to about 65 mg.
A smoking article comprising a fuel element (10; 24) and a physically separate aerosol generating means (12; 90; 96) according to one of the preceding claims.
A smoking article according to claim 17, wherein above about 2 weight percent of the aerosol forming substance carried on the substrate (13; 38; 54; 66) are delivered to the user as WTPM.
A smoking artivle according to claim 18, wherein above about 15 weight percent of the aerosol forming substance carried on the substrate (13; 38; 54; 66) are delivered to the user as WTPM.
A smoking article according to claim 19, wherein above about 20 weight percent of the aerosol forming substance carried on the substrate (13; 38; 54; 66) are delivered to the user as WTPM.