NO171823B - ROEYKEARTIKKEL - Google Patents

Abstract

The cigarette has a carbonaceous fuel element. A separate aerosol generator has a substrate bearing an aerosol forming material. The fuel element and substrate are arranged in a conductive relationship, so that the heat-stable substrate receives conductive heat transfer throughout the burning time of the fuel element. The fuel element is less than 30mm in length, with a density of at least 5 g/cc. An insulation material can surround part of the fuel element. The insulation is resilient and at least 15 mm thick. The cigarette also has a mouthpiece.

Description

The present invention relates to a smoking article comprising a combustible fuel element and a physically separate aerosol-forming device containing a substrate containing an aerosol-forming material, the aerosol-forming device being located longitudinally behind the fuel element.

The smoking article produces an aerosol that resembles tobacco smoke and contains a minimal amount of incompletely combusted or pyrolysis products.

Many smoking articles have been proposed over the years, especially over the past 20 to 30 years, but none of these products have ever achieved any sales success.

Despite decades of interest and effort, there is still no smoking article on the market that provides the gains and benefits found in regular cigarette smoking without providing significant amounts of incompletely combusted and pyrolysis products.

The present invention relates to a smoking article which can produce significant amounts of aerosol, both initially and throughout the product's useful life, without significant thermal breakdown of the aerosol generator and without the presence of significant pyrolysis or incompletely burned products, and preferably without significant amounts of sidestream smoke. Smoking articles according to the present invention can provide the user with the sensations and benefits of cigarette smoking without burning tobacco.

These and other advantages are achieved by the fact that the smoking article additionally contains a heat-conducting element which is designed and arranged to transfer heat from the fuel element to the aerosol generating device throughout the substantial burning time of the fuel element, and which is either in contact with or overlaps at least part of the fuel element and the aerosol forming device.

The fuel element is preferably a carbonaceous material. After ignition, the fuel element provides heat which is used to volatilize the aerosol-forming substance or substances in the aerosol-forming device. These volatile materials are then drawn towards the end of the mouth, especially during puffs, and into the consumer's mouth similar to the smoke from a regular cigarette.

The smoking article according to the present invention is normally equipped with a mouthpiece containing elements such as an elongated passage for delivering volatile material produced by the aerosol forming device to the consumer. Advantageously, the article has the same overall dimensions as a regular cigarette, and as a result the mouthpiece and aerosol delivery device extend normally and more than half the length of the article. Alternatively, the fuel element and aerosol generating device may be manufactured without a built-in mouthpiece or aerosol delivery device for use with a separate, disposable or reusable mouthpiece.

The smoking article according to the present invention can also contain a filling or plug of tobacco which can be used to add a tobacco flavor to the aerosol. Preferably, the tobacco is placed at the mouth end of aerosol-forming devices, or it may be mixed with the carrier for the aerosol-forming substance. Flavorings can also be introduced into the article to provide the aerosol that goes to the smoker soon.

Preferred embodiments of the invention are capable of providing at least 0.6 mg of aerosol, measured as wetted total particulate matter, in the first three puffs of smoking under FTC smoking conditions. (FTC smoking conditions consist of 2 second puffs (35ml total volume) separated by 58 seconds of smoldering). Even more strongly preferred embodiments of the invention are capable of delivering 1.5 mg or more of aerosol in the first three puffs. Preferably, embodiments of the invention are capable of providing 3 mg or more of aerosol in the first three puffs of smoking under FTC smoking conditions. Furthermore, the preferred embodiments of the invention an average of at least approx. 0.8 mg moistened total particulate matter per drag at least approx. six drafts, preferably at least approx. ten puffs under FTC smoking conditions.

The smoking article according to the present invention is also capable of providing an aerosol that is chemically simple, in that it consists mainly of carbon oxides, air, water and the aerosol carrying any desired flavors or other desired volatile materials and trace elements of other materials. The aerosol preferably has no significant mutagenic activity according to the aforementioned Ames test. In addition, the article can be made practically ashless, so that the user does not have to remove any ash during use.

As used here, and only for the purpose of the invention, "aerosol" is defined to contain vapors, gases, particles and the like, both visible and invisible, and especially such components that the smoker experiences as "smoke-like" formed by the action of heat from the burning fuel element on substances in the aerosol forming device or otherwise in the article. As defined in this way, "aerosol" also includes volatile flavoring agents and/or pharmacologically or physiologically active agents, regardless of whether they produce a visible aerosol.

As used herein, the phrase "conductive heat exchange ratio" is defined as the physical arrangement of the aerosol forming device and the fuel element whereby heat is transferred by conduction from the burning fuel element to the aerosol forming device, essentially through the burning time of the fuel element. Conductive heat exchange conditions can be achieved by placing the aerosol forming device in contact with the fuel element and close to the burning part of the fuel element, and/or by using a conductive element to conduct heat from the burning fuel to the aerosol forming device. Preferably, both methods are used to provide heat conduction transfer.

As used here, the term "carbonaceous" device includes primarily carbon.

As used herein, the term "insulating agents" refers to all materials that primarily act as insulators. Preferably these materials do not burn during use, but they may contain slow burning carbons and similar materials as well as materials which fuse during use such as low temperature grades of glass fibres. The insulators have a thermal conductivity in g-cal/(sec.) (cm<2>) (°C/cm), of less than approx. 0.05, preferably less than approx. 0.02, preferably less than approx. 0.005. See Hackh's Chemical Dictionary, 34 (4th ed., 1969) and Lange's Handbook of Chemistry, 10, 272-274 (little ed., 1973).

The smoking article according to the present invention is described in more detail in the accompanying drawings and the detailed description of the invention that follows.

Fig. 1 to 7 are longitudinal sections of different embodiments of the invention;

fig. IA is a cross-section of the embodiment of fig. 1 seen along the line IA-IA in fig. 1;

fig. 2A is a longitudinal section of a modified, tapered fuel element in the embodiment of FIG. 2;

fig. 3A is a cross-section of the embodiment of FIG. 3 seen along lines 3A-3A in fig. 3; and

Fig.8 shows the average peak temperature profile for the smoking article in Example 5 during use.

The embodiment of the invention illustrated in fig. 1, which preferably has the diameter of an ordinary cigarette, contains a short, combustible carbonaceous fuel element 10, adjacent to the impact aerosol generating device 12, and a foil-covered paper tube 14, which forms the mouth end 15 of the article. In this embodiment, the fuel element 10 is a "blow pipe" tar coal, i.e. charred wood, which is provided with five longitudinal holes 16. See Figure IA. The fuel element 10 which is approx. 20 mm long, can optionally be wrapped in cigarette paper to improve the ignition of the tar coal fuel. This paper can be treated with known fuel additives.

The aerosol-forming device 12 contains several glass balls 20 coated with an aerosol-forming substance or

substances such as glycerol. The glass balls are held in place by a porous disk 22, which may be made of cellulose acetate. This disc can be equipped with a number of edge pits 24 which form passages between the disc and the foil-covered tube 14.

The foil-covered paper tube 14, which forms the mouth end of the article, surrounds the aerosol generating device 12 and the rear, non-igniting end of the fuel element 10. The tube also forms an aerosol delivery passage 26 between the aerosol generating device 12 and the mouth end 15 of the article.

The presence of the foil-lined tube 14, which connects the non-igniting end of the fuel 10 to the aerosol generator 12, also increases the heat transfer to the aerosol generator. The foil also helps to extinguish the cone of fire. When only a small amount of the unburned fuel remains, the heat loss through the foil acts as a heat sink which helps to extinguish the cone of fire.

The foil used in this article is preferably an aluminum foil with a thickness of 0.0089 mm, but the thickness and/or type of metal used can be varied to achieve any desired degree of heat transfer. Other types of heat-conducting elements such as Grafoil from Union Carbide can also be used.

The article illustrated in fig. 1 also contains a possible mass or plug of tobacco 28 to give the aerosol more flavor. This tobacco filling 28 can be placed at the mouth end of the disk 22 as shown in fig. 1, or it can be placed between the glass balls 20 and the disk 22. It can also be placed in the passage 26 in a place away from the aerosol generator 12.

In the embodiment shown in fig. 2, the short fuel element 10 is a pressed carbon rod or plug, approx. 20 mm long, which is provided with an axial hole 16. Alternatively, the fuel may be formed of carbonized fibers and preferably also provided with an axial passage corresponding to the hole 16. In this embodiment, the aerosol generating device 12 contains a thermally stable conductive carbonaceous substrate 30 such as a plug of porous carbon, which is impregnated with an aerosol-forming substance or substances. This substrate can be provided with an optional axial passage 32 as shown in fig. 2. This embodiment also contains a mass of tobacco 28 which is preferably placed on the mouth end of the substrate 30. For the sake of appearance, the article also contains an optional highly porous cellulose acetate filter 34 which may be provided with edge grooves 36 to provide passage for the aerosol-forming substance between the filter 34 and the foil tube 14. As shown in fig. 2A, the ignition end 11 of the fuel element can optionally be tapered to facilitate ignition.

The embodiment of the invention illustrated in fig. 3 contains a short combustible carbonaceous fuel element 10 connected to the aerosol generating device 12 by a heat-conducting rod 99 and a foil-lined paper tube 14, which also leads to the mouth end 15 of the article. In this embodiment, the fuel element 10 may be blowpipe tar coal or a pressed or extruded carbon rod or plug or other carbonaceous fuel source.

Aerosol-forming agents 12 contain a thermally stable carbonaceous substrate 30 such as a plug of porous carbon which is impregnated with an aerosol-forming substance or substances. This embodiment contains a void 97 between the fuel element 10 and the substrate 30. The portion of the foil-clad tube 14 surrounding this void contains several holes 100 on the edge which enable sufficient air to enter the void to provide suitable pressure drop.

As shown in fig. 3 and 3A, the heat conducting device includes a conductive rod 99 and the foil-clad tube 14. The rod 99, preferably formed of aluminum, has at least one, preferably from 2 to 5 edge grooves 96 therein to enable the passage of air within the substrate. The article in fig. 3 has the advantage that the air entering void 97 contains less carbon oxidation products because it is not drawn through the burning fuel.

The embodiment as illustrated in fig. 4 contains a fibrous carbon fuel element 10 such as carbonized cotton or rayon. The fuel element contains a single axial hole 16. The substrate 38 of the aerosol generator is a granular, thermally stable carbon. A tobacco mass 28 is located immediately behind the substrate. This article is provided with a cellulose acetate tube 40 instead of the foil-clad tube of previous embodiments. This tube 40 contains an annular part 42 of cellulose acetate string which surrounds an optional plastic, for example polypropylene tube 44. At the mouth end 15 of this element there is a low efficiency cellulose acetate filter plug 45. The entire length of the article is wrapped in cigarette-type paper 46. A cork or white ink coating 48 can be used on the mouth end to simulate a tip. A foil strip 50 is located on the inside of the paper towards the fuel end of the article. This strip preferably runs from the rear of the fuel element to the mouth end of the tobacco filling 28. It may be in one piece with the paper, or be a separate piece applied before the paper wrapping.

The embodiment in fig. 5 is similar to that in fig. 4. In this embodiment, the aerosol-forming device 12 is formed of an aluminum macrocapsule 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 macrocapsule 52 is crimped at its ends 58, 60 to contain the material and prevent migration of the aerosol generator. The crimped end 58 of the fuel end preferably abuts the rear end of the fuel element to provide conductive heat transfer. A void 62 formed by the end 58 also helps prevent migration of the aerosol former to the fuel. Longitudinal passages 59 and 61 are arranged to enable the passage of air and the aerosol-forming substance. The macrocapsule 52 and the fuel element 10 can be combined with an ordinary cigarette paper 47 as illustrated in the drawing, with a perforated ceramic paper or a foil strip. If cigarette paper is used, at a strip 64 near the rear end of the fuel be pressed or treated with sodium silicate or other known materials which cause the paper to extinguish. The entire length of the article is wrapped with ordinary cigarette paper 46.

Fig. 6 illustrates another embodiment with a pressed carbon fuel plug 10. In this embodiment, the fuel element has a tapering ignition end 11 for easier ignition and a tapering rear end 9 for easier insertion into a tubular foil wrapping 66. The abutments against the rear end of the fuel element have one an aluminum disk 68 with a central hole 70. A second, optional aluminum disk 72 with a hole 74 is located at the mouth end of the aerosol generator 12. Between is a zone 76 of a particulate substrate and a zone 78 of tobacco. The foil wrapper 66 in which the fuel element is mounted extends backwards past the second aluminum disc 72. This embodiment also contains a hollow cellulose acetate rod 42 with an inner polypropylene tube 44 and a cellulose acetate filter plug 45. The entire length of the article is preferably wrapped with cigarette paper 46.

The embodiment shown in fig. 7 illustrates the use of a substrate 80 embedded in a large cavity 82 in the fuel element 10. In this embodiment, the fuel element is preferably formed from an extruded carbon, and the substrate 80

generally a relatively stiff, porous material. The entire length of the article is wrapped in plain cigarette paper 46. This embodiment may also include a foil strip 84 to connect the fuel element 10 to the cellulose acetate tube 40 and assist in extinguishing the fuel.

After ignition of one of the aforementioned embodiments, the fuel element burns to provide the heat used to volatilize the aerosol-forming substance or substances present in the aerosol-forming device. These volatile materials are then drawn towards the end of the mouth, especially during puffs, and into the smoker's mouth like the smoke from a normal cigarette.

Because the fuel element is preferably relatively short, the hot, burning cone of fire is always close to the aerosol generating body, maximizing heat transfer to the aerosol generating device, and resulting production of aerosol, especially when the preferred heat conducting element is used. In addition, the preferred insulating element tends to confine, direct and concentrate the heat towards the central core of the article thereby increasing the heat transferred to the aerosol-forming substance.

Because the aerosol-forming substance is physically separated from the fuel element, it is exposed to significantly lower temperatures than those present in the burning cone of fire. This minimizes the possibility of thermal degradation of the aerosol generator. This also leads to aerosol production during draft, but little or no aerosol production during smoldering. In addition, the use of the preferred carbonaceous fuel elements and a physically separate aerosol generating device eliminates the occurrence of significant pyrolysis or incomplete combustion products and avoids the formation of significant sidestream smoke.

Due to the small size and burning characteristics of the preferred carbonaceous fuel element used in the present invention, the fuel element normally begins to burn over substantially its entire exposed length within a few puffs. Thus, the part of the fuel element close to the aerosol generating device becomes hot quickly, which significantly increases the heat transfer to the aerosol generating device, especially during the early and intermediate drafts. Because the preferred fuel element is short, there is never a long section of non-burning fuel acting as a heat sink, as was common in earlier thermal aerosol articles. Heat transfer and therefore aerosol release is also increased by the use of holes through the fuel, which draw hot air to the aerosol generator, especially during drafts.

In the preferred embodiments of the invention, the short carbonaceous fuel element, the heat conduction element, the insulation devices and the passages in the fuel cooperate with the aerosol generator to provide a system capable of producing significant amounts of aerosol after practically every puff. The close proximity of the fire cone to the aerosol generator leads after a few puffs together with the insulation device to a high heat release both during puffs and during the relatively long smoldering period between puffs.

Without wishing to be bound by theory, it is believed that the aerosol generating devices are maintained at a relatively high temperature between drafts and that the additional heat given off during drafts, which is significantly increased by the hole or holes in the fuel element, is primarily used to vaporize the aerosol-forming substance . This increased heat transfer makes more efficient use of the available fuel energy, reduces the amount of fuel required, and helps to release early aerosol. Furthermore, the conductive heat transfer used in the present invention is assumed to reduce the carbon combustion temperature, which is further assumed to reduce the CO/C02 ratio in the combustion products arising from the fuel. See, for example, G. Hagg, General Inorganic Chemistry, p. 592 (John Wiley & Sons, 1969).

By corresponding choice of fuel element, insulation jacket, paper wrapping and heat conduction device, it is also possible to control the combustion properties of the fuel source. This gives the opportunity to control heat transfer to the aerosol generator, which in turn is linked to the number of puffs and/or the amount of aerosol delivered to the smoker.

In general, the combustion elements that can be used in the invention are smaller than approx. 30 mm long. Advantageously, the fuel element is approx. 20 mm or less, preferably approx. 15 mm or less long. Advantageously, the diameter of the fuel element is between approx. 3 and 8 mm, preferably approx. 4 to 5 mm. The density of the fuel elements used here has varied from approx. 0.5 g/cm<2> to approx. 1.5 g/cm<2>. Preferably, the density is greater than 0.7 g/cm<2>, preferably greater than 0.8 g/cm<2>. Preferably, the fuel is equipped with one or more longitudinal holes such as the holes 11 in fig. 1 to 5. These holes provide porosity and increase early heat transfer to the substrate by increasing the amounts of hot gases reaching the substrate.

The preferred fuel elements used here are primarily formed from a carbonaceous material. Carbonaceous fuel elements are preferably from c. 5 to 15 mm, especially from approx. 8 to 12 mm long. Carbon-containing fuel elements with these properties are sufficient to provide fuel for at least approx. 7 to 10 puffs, the normal number of puffs normally obtained from smoking a regular cigarette under FTC conditions.

Preferably, the carbon content of such a fuel element is at least 60-70%, preferably at least approx. 80% or more of the weight. Excellent results have been achieved with fuel cells with a carbon content of over approx. 85% by weight. Fuels with high carbon content are preferred because they produce minimal pyrolysis and incomplete combustion products, little or no visible sidestream smoke, and minimal ash and have high heating capacity. However, fuel cells with low carbon content, for example approx. 50-65% by weight, within the scope of the invention, especially when a non-burning inert filter is used.

Also, if not preferred, other fuel materials can be used such as tobacco, tobacco substitutes and the like, provided they generate and conduct sufficient heat to the aerosol forming device to provide the desired aerosol amount from the aerosol forming material as discussed above. The density of the fuel used should be above approx.

0.5 g/cm<2>, preferably over approx. 0.7 g/cm<2>, which is higher than the densities normally used in ordinary smoking articles. When such other materials are used, it is strongly preferred to introduce carbon into the fuel, preferably in amounts of at least about 20-40% by weight, or at least approx. 50% by weight and preferably at least approx. 65-70% by weight, with the rest consisting of other fuel components including possible binders, combustion modifiers, moisture etc.

The carbonaceous materials used in or as the preferred fuel may be derived from virtually any of the numerous carbon sources that will be known to one skilled in the art. Preferably, the carbonaceous material is obtained by pyrolysis or carbonization of cellulosic materials such as wood, cotton, rayon, tobacco, coconuts, paper and the like, although carbonaceous materials from other sources may be used.

In most cases, the carbonaceous fuel element should be able to be ignited with an ordinary cigarette lighter without the use of an oxidizing agent. Combustion characteristics of this type can generally be obtained from a cellulose material that has been pyrolysed at temperatures between approx. 400°C and 1000°C, preferably between approx. 500°C and 950°C through an inert atmosphere or under a vacuum. The pyrolysis time is not believed to be critical as long as the temperature in the middle of the pyrolyzed mass has reached the aforementioned temperature range for at least 5 minutes. However, a slow pyrolysis using gradually increasing temperatures over several hours is believed to produce a smoother material with a higher carbon yield.

However, undesirable in most cases, carbonaceous fuel elements which require the addition of an oxidizing agent to make them ignitable with a cigarette lighter are within the scope of the invention as are carbonaceous materials which require the use of a glow suppressant or other type of combustion modifying agent. Such combustion modifying agents are described in many patents and publications and are known to one of ordinary skill in the art.

Most of the preferred carbonaceous fuel elements used in the invention are essentially free of volatile organic material. This means that the fuel element is not intentionally impregnated or mixed with significant amounts of volatile organic materials such as volatile aerosol-forming or flavoring agents, which could break down in the burning fuel. However, small amounts of water that is naturally adsorbed by the fuel can be present. In similar ways, small amounts of aerosol-forming substances can move from the aerosol-forming device and thus also be present in the fuel element.

A preferred carbonaceous fuel element is a pressed or extruded carbon mass prepared from carbon and a binder by conventional pressure forming or extrusion techniques. A preferred activated carbon for such a fuel element is PCB-G, and a preferred non-activated carbon is PXC, both available from Calgon Carbon Corporation, Pittsburgh, PA. Other preferred carbons for pressure forming and/or extrusion are made from pyrolyzed cotton or pyrolyzed paper.

The binders that can be used in the production of such a fuel element are well known in the field. A preferred binder is sodium carboxymethyl cellulose (SCMC) which can be used alone, which is preferred, or in conjunction with materials such as sodium chloride, vermiculite, bentonite, calcium carbonate and the like. Other useful binders are gums such as guar gum and other cellulose derivatives such as

methyl cellulose and carboxymethyl cellulose (CMC).

A wide range of binder concentrations can be used. Preferably, the amount of binder is limited to minimize the binder's contribution to unwanted combustion products. On the other hand, sufficient binder must be included to hold the fuel element together during manufacture for use. The amount used will thus depend on the cohesiveness of the carbon in the fuel element.

If desired, the aforementioned fuel elements can be pyrolysed after formation, for example to approx. 650°C for 2 hours to transfer the binder into carbon and thereby form a virtually 100% carbon fuel element.

The fuel elements used in the present invention may also contain one or more additives to improve combustion, thus up to approx. 5 wt% sodium chloride to improve smoldering properties and as a glow retardant. Also up to approx. 5%, preferably 1 to 2% by weight of potassium carbonate can be included to improve flammability. Additives to improve physical properties such as clays, for example kaolins, serpentines, attapulgites and the like can also be used.

Another carbonaceous fuel element is a carbon fiber fuel that can be produced by carbonizing a fibrous precursor such as cotton, rayon, paper, polyacrylonitrile and the like. In general, pyrolysis of wood from approx. 650°C to 1000°C, preferably approx. 950°C for 30 minutes in an inert atmosphere or vacuum sufficient to produce a suitable carbon fiber with good burning properties. Combustion modifying additives can also be added to these fibrous fuels.

The aerosol-forming agents used in the invention are physically separated from the fuel element. Physically separated means that the substrate, container or chamber containing the aerosol-forming materials is not mixed with, or part of, the burning fuel element. As previously noted, this device helps to reduce or eliminate thermal decomposition of the aerosol-forming substance and the presence of sidestream smoke. Although the aerosol-forming devices are not part of the fuel, they are in a heat-conducting relationship with the fuel element, and preferably abut or lie close to the fuel element.

Preferably, the aerosol-forming devices contain one or more thermally stable materials containing one or more aerosol-forming substances. As used here, a thermally stable material is one that can withstand the high temperatures, for example 400°C-600°C, which exist near the fuel without deposition or burning. The use of such a material is believed to help maintain the simple "smoke" chemistry of the aerosol as evidenced by the lack of Ames activity in the preferred embodiments. If not preferred, other aerosol-forming devices such as heat-breakable microcapsules or solid aerosol-forming substances within the scope of the invention, provided they are capable of releasing sufficient aerosol-forming vapors to satisfy similar tobacco smoke.

Thermally stable materials that can be used as a substrate or carrier for the aerosol-forming substance are well known to a person skilled in the art. Useful substrates should be porous and must be capable of retaining an aerosol-forming compound when not in use and capable of releasing a potential or aerosol-forming vapor upon heating of the fuel element.

Useful thermally stable materials are thermally stable adsorbent carbons such as carbons of porous quality, graphite, activated or non-activated carbons and the like. Other suitable materials are inorganic solids such as ceramic materials, glass, aluminum oxide, vermiculite, clay such as bentonite and the like. The most frequently preferred substrate materials are carbon filters, fibers and mats, activated carbons and porous carbons such as PC-25 and PG-60 from Union Carbide as well as SGL carbon from Calgoh.

Depending on the individual aerosol-forming devices used here, the composition and configuration of these can generally be selected from particulate, fibrous, porous blocks, solid blocks with one or more axial passages through them and the like. Substrates, especially particulate ones, can be placed in a container, preferably formed of a metal foil.

Aerosol-forming agents used in the invention are normally no more than approx. 60 mm, preferably no more than 30 mm, preferably no more than 15 mm from the ignition end of the fuel element. The aerosol generator can vary in length from approx. 2 mm to approx. 60 rna, 'preferably from approx. 5 mm to 40 mm and preferably from approx. 20mm to 35mm. If a non-particulate substrate is used, one or more holes may be provided to increase the surface area of the substrate, and to increase airflow and heat transfer.

The aerosol-forming substance or substances used in the invention must be able to form an aerosol at the temperatures present in the aerosol-forming device when heating the burning fuel element. Such substances will preferably consist of carbon, hydrogen and oxygen, but they may contain other materials. The aerosol-forming substances can be in solid, semi-solid or liquid form. The boiling point of the substance and/or mixture of substances can vary up to approx. 500°C. Substances with such properties are polyhydric alcohols such as glycerol and propylene glycol, as well as aliphatic esters of mono-, di- or polycarboxylic acids such as methyl stearate, dodecanedioate, dimethyl tetradodecanedioate and others.

Preferably, the aerosol-forming substances will contain a mixture of a high-boiling substance with a low vapor pressure and a low-boiling substance with a high vapor pressure. In earlier drafts, a low-boiling substance will thus produce most of the initial aerosol, while when the temperature in the aerosol generator increases, the high-boiling substance will produce most of the aerosol.

The preferred aerosol-forming substances are polyhydric alcohols or mixtures of polyhydric alcohols. Particularly preferred aerosol generators are selected from glycerol, propylene glycol, triethylene glycol or mixtures thereof.

The aerosol-forming substance can be dispersed on or in the aerosol-forming device in a sufficient concentration to permeate or coat the substrate, carrier or container. For example, the aerosol-forming substance can be applied at full strength or in a diluted solution by dipping, spraying, vapor deposition or similar techniques. Solid aerosol-forming constituents can be mixed with the substrate and distributed evenly through it prior to formation.

Although filling with aerosol-forming substance will vary from carrier to carrier and from aerosol-forming substance to aerosol-forming substance, the amount of liquid aerosol-forming substances can generally vary from approx. 20 mg to approx.

120 mg, preferably from approx. 35 mg to 85 mg, and preferably from approx.

45 mg to 65 mg. As much as possible of the aerosol generator initially placed on the aerosol generating device should be delivered to the user as WTPM. Preferably issued over approx. 2% by weight, or over approx. 15% by weight and preferably over approx. 20% by weight of the aerosol that was first placed on the aerosol forming device of the smoker which

WTPM.

The aerosol-forming agents may also contain one or more volatile flavoring agents such as menthol, vanillin, artificial coffee, tobacco extracts, nicotine, caffeine, spirits and other agents that can give the aerosol flavor. It may also contain any other desirable volatile solid or liquid materials.

As previously pointed out, the smoking article according to the present invention can also contain a filling or plug of tobacco which can be used to give the aerosol a tobacco flavour. Preferably, the tobacco is placed in the mouth end of the aerosol-forming device, or can be mixed with the carrier for the aerosol-forming substance. The flavoring agent can also be incorporated into the article to give the aerosol delivered to the smoker flavor.

If a tobacco filling is used, hot vapors pass through the tobacco layer to extract and vaporize the volatile constituents in the tobacco without the tobacco having to burn. Thus, the smoker of this smoking article receives an aerosol containing the quality and flavors of natural tobacco without the combustion products produced by a regular cigarette.

Alternatively, these facultative means may be placed between the aerosol-forming device and the mouth end, such as in a separate substrate or chamber in the passage leading from the aerosol-forming device to the mouth end, or in the facultative tobacco filling. If desired, these volatile agents can replace some or all of the aerosol-forming substance so that the article emits a non-aerosol flavor or other material to the smoker.

Articles of the type described here can be used or can be modified for use as drug delivery articles for the delivery of volatile pharmacological or physically active materials such as ephedrine, metaproterenol, terbutaline or the like.

The heat-conducting element that is preferably used in the present invention is often a metal foil such as aluminum foil varying in thickness from less than approx.

0.01 mm to approx. 0.1 mm or more. The thickness and/or type of conductive material can be varied to achieve virtually any desired degree of heat transfer. As shown in the illustrated embodiments, the thermally conductive element preferably contacts or overlaps a portion of the fuel element and the aerosol-forming device, and may form the container enclosing the aerosol-forming substance.

In most embodiments of the invention, the combustion/aerosol generation combination will be attached to a mouthpiece such as a foil-covered paper or cellulose acetate/plastic tube illustrated in the figures, although a mouthpiece may be arranged separately, for example in the form of a cigarette holder. This element of the article provides passageways that channel the vaporized aerosol-forming substance into the smoker's mouth. Due to the length, preferably approx. 50 to 60 mm or more, it also keeps the hot cone of fire away from the smoker's mouth and fingers.

Suitable mouthpieces should be inert with respect to the aerosol-forming substances, should have a water or liquid tight inner layer, should provide minimal aerosol loss by condensation or filtration, and should be able to withstand temperatures at the interface with the article's other elements. Preferred mouthpieces are the foil-covered tubes of Figures 1 to 3 and the cellulose acetate tube used in the embodiments of Figures 4 to 9. Other suitable mouthpieces will be obvious to one skilled in the art.

The mouthpieces according to the invention may contain a possible "filter" tip, which is used to give the article the appearance of the usual filter cigarette. Such filters include low-density cellulose acetate filters and hollow or deflected plastic filters such as those made of polypropylene. In addition, the entire length of the article or part of it may be wrapped in cigarette paper.

The aerosol produced by the preferred articles according to the present invention are chemically simple, consisting mainly of air, carbon oxides, the aerosol carrying the desired flavors or other volatile materials, water and trace amounts of other materials. The moist total particulate matter (WTPM) produced by the preferred articles according to the invention has no mutagenic activity as measured by the Ames test, i.e. there is no appreciable dose-dependent relationship between the WTPM in the present invention and the number of revertants appearing in standard test microorganisms exposed for such products. According to the Ames test, a significant dose-dependent reaction indicates the presence of mutagenic materials in the products examined. See Ames et al., Mut. Res., 31:347-364 (1975); Nagas et al., Mut. Res., 42:335

(1977).

A further advantage of the preferred embodiments of the present invention is the relative lack of ash produced during use as compared to ash from a normal cigarette. As the preferred carbon fuel source is burned, it is primarily converted to oxides of carbon with relatively little ash formation, and thus there is no need to dispose of ash while the article is in use.

The smoking article according to the present invention will be illustrated in more detail with reference to the following examples which contribute to the understanding of the present invention, but must not be regarded as limiting it. All percentages given here, unless otherwise stated, are % by weight. All temperatures are expressed in degrees Celsius and are uncorrected. In all cases, the smoking article has a diameter of approx. 7 to 8 mm, the diameter of a regular cigarette.

Example 1

A smoking article was constructed according to the embodiment of FIG. l. The fuel element was a 25 mm long piece of blowpipe tar coal with 1.02 mm longitudinal passages made with a No. 60 drill bit. The tar coal weighed 0.375 g. The fuel element was wrapped in ordinary treated cigarette paper. The substrate was 500 mg glass beads of 1.63 mm average diameter with two drops, approx. 50 mg, glycerol coating on the surface. When they were wrapped in the tube, this substrate was approx. 6.5 mm long. The foil-clad tube consisted of a 0.0089 mm layer of aluminum foil inside a 0.108 mm layer of white spiral-twisted paper. This tube surrounded the rear 5 mm of the fuel element. A short (8 mm) piece of cellulose acetate with four grooves around the edge was used to hold the glass beads against the fuel source. An additional cellulose acetate filter piece with grooves 8 mm long was inserted into the mouth end of the tube to give the appearance of a regular cigarette. The total length of the article was approx. 70 mm.

Models of this type produced significant aerosol on the ignition puff, reduced amounts of aerosol on puffs two and three, and good release of aerosol on puffs four through nine. Models of this type generally gave approx. 5-7 mg wet total particulate matter (WTPM) by machine smoking during FTC smoking procedures with a 35 ml puff volume, a 2 second puff duration, and a 60 second puff frequency.

Example 2

A. Four smoking articles were constructed with 10 mm long pressing carbon fuel elements and glass ball substrates. The fuel elements were formed from 90% PCB-G and 10% SCMC at approx. 2273 kg load with the tapered ignition end illustrated in fig. 2A. A single 1.02 mm hole was formed down the center of each element. Three of the four fuel sources were wrapped with 8 mm wide strips of ordinary cigarette paper. The fuel elements were inserted approx. 2 mm in 70 ml long sections of foil-lined tubing described in Example 1. Glass beads coated with the indicated amount of glycerol in the following table were inserted into the open end of the foil-lined tubing and held against the fuel element by 5 mm long foamed polypropylene filters with a series of longitudinal ridges. A 5 mm long low efficiency cellulose acetate filter piece was inserted into the mouth end of each article. These articles were machine smoked under FTC smoke conditions and the wet total particulate matter (WTPM) was collected on a series of Cambridge pads. The results of these experiments are shown in table I.

B. Three smoking articles similar to those described in Example 2A were constructed with 20 mm long blow pipe tjaere charcoal fuel elements of the type described in Example 1. These articles were machine smoked under FTC smoking conditions, and at the WTPM were collected on a range of Cambridge cushions. The results of these tests are reported in Table II.

EXAMPLE 3

A. Four smoking articles were constructed as shown in fig. 2 with a 10 mm pressed carbon fuel element with the tapered ignition end illustrated in FIG. 2A. The fuel element was made of 90% PCB-G carbon and 10% SCMC at approx. 2273 kg load. A 1.02 mm hole was drilled down through the center of the element. The substrate for the aerosol generator was cut and shaped from PC-25, a porous carbon sold by Union Carbide Corporation, Danbury, CT. The substrate in each article was approx. 2.5 mm long and approx. 8 mm in diameter. It was coated with an average of approx. 27 mg of a 1:1 propylene-glycol-glycerol mixture. The foil-clad mouthpiece tube of the same type as used in Example 1 enclosed the rear 2 mm of the fuel element and substrate. A plug of Burley tobacco, approx. 100 mg, was placed against the mouth end of the substrate. A card, approx. A 5-9 mm deflected polypropylene filter piece was placed in the mouth end of the foil-lined tube. A 32 mm length of a cellulose acetate filter with a hollow polypropylene tube in the core was placed between the tobacco and the filter piece. The total length of each article was approx. 78 mm.

B. Six additional articles were constructed essentially as in Example 3A, but the substrate length was increased to 5 mm, and a 1.02 mm hole was drilled through the substrate. In addition, these particles did not have a cellulose acetate/polypropylene tube. About. 42 mg of the propylene-glycol-glycerol mixture was placed on the substrate. In addition, two plugs were Burley tobacco, approx. 100-150 mg each, used. The first was placed against the mouth end of the substrate, and the second was placed against the filter piece. C. Four additional articles were concentrated essentially as in Example 3A, except that an approx. 100 mg smoke channel cured tobacco containing approx. 6 wt% diammonium monohydrogen phosphate was used in place of the burley tobacco plug. D. The smoking articles of Examples 3A-C were examined using the standard Ames test. See Ames, et al., Mut. Res., 42:335 (1977), and 113:173-215 (1983). Samples 3A and C were "smoked" on a conventional cigarette smoking machine using the conditions of a 35 ml puff volume, a 2 second puff duration and a 30 second puff frequency for ten puffs. The smoking article of Example 3B was smoked in the same manner, except that a 60 second draw frequency was used. Only one filter pad was used for each group of articles. This gave the following wet total particulate matter (WTPM) for the indicated groups of articles:

The filter pad for each of the above examples containing the collected WTPM was shaken for 30 minutes in DMSO to dissolve the WTPM. Each sample was then diluted to a concentration of 1 mg/ml and used "as is" in the Ames assay. Using the method of Nagas et al., Mut. Res., 42:335-342 (1977), 1 mg/ml concentrations of WTPM were mixed with the S-9 activation system plus the standardized Ames bacteria cells and incubated at 37°C for 20 minutes. The bacterial strain used in this Ames assay was Salmonella typhimurium, TA 98. See Purchase et al., Nature, 264:624-627 (1976). The mixture was then added to agar and plates were prepared. The agar plates were incubated for 2 days at 37°C, and the resulting cultures were counted. Four plates were run for each dilution, and the standard deviations of the colonies were compared to a pure DMSO control culture. As shown in Table III, there was no mutagenic activity caused by the WTPM obtained from any of the smoking articles examined. This can be confirmed by comparison with the average number of revertants per plate with mean number of revertants obtained from the control (0 fiq WTPM/plate) . For mutagenic samples, the average number of revertants per plate increase with increasing doses. Example 3B

Example 3C

EXAMPLE 4

Five smoking articles were constructed as shown in fig. 2. Each article had a 10 mm compressed carbon fuel source as described in Example 3A. This fuel element was inserted 3 mm into one end of a 70 mm long aluminum foil-clad tube of the type described in Example 1. A 5 mm long carbon-filled substrate, cut from rayon carbon felt sold by Fiber Materials, Inc., was contacted against the fuel source. This substrate was loaded with an average of approx. 97 mg of a 1:1 mixture of glycerol and propylene glycol, approx. 3 mg of nicotine, and approx. 0.1 mg of a mixture of flavourings. A 5 mm long piece of mixed tobacco was placed against the mouth end of the substrate. A 5 mm long cellulose acetate filter piece was placed in the mouth end of the foil-lined tube.

These articles were machine smoked under FTC conditions.

The aerosol from these articles was collected on a single Cambridge pad (13 3.3 mg WTPM), diluted in DMSO to a final concentration of 1 mg WTPM per ml and assayed for Ames activity as described in Example 3D using each of the following strains: Salmonella typhimurium TA 1535, 1537, 1538, 98 and 100. As shown in Table IV, there was no mutagenic activity caused by WTPM collected from the examined articles.

EXAMPLE 5

A smoking article was constructed as shown in fig. 2 with one

10 mm pressed carbon fuel plug of a shape shown in fig. 2A, but without tobacco. The fuel element was made of a mixture of 90% PCB-G activated carbon and 10% SCMC as a binder at 2273 kg applied pressure. The fuel element was provided with a 1.02 mm longitudinal passage. The substrate was a 10 mm long porous carbon plug made of Union Carbide's PC-25. It was fitted with a 0.74 mm drilled axial hole, and was coated with 40 mg of a (1:1) mixture of propylene glycol and glycerol. As in example 1, the foil-clad tube surrounded the rear 2 mm of the fuel element and formed the mouth end piece. The article did not have a filter tip, but was wrapped in ordinary cigarette paper. The entire length of the article was 80 mm.

The average peak temperatures for this article are shown for both "draft" and "smolder" in fig. 10. As shown, the temperature constantly decreases between the rear end of the fuel element and the mouth end. This guarantees that the smoker does not get an unpleasant burning sensation when using the product according to

the invention.

EXAMPLE 6

A smoking article was constructed according to the embodiment of FIG. 3. The fuel element was a 19 mm long piece of blow pipe tar coal, but without longitudinal passages. Embedded 15 mm into the fuel element was a 3.2 mm diameter aluminum rod, 28 mm long. Four 9 mm x 0.64 mm edge grooves, spaced 90° apart, were cut into the portion of the aluminum rod that penetrates the substrate. The substrate was Union Carbide PC-25 carbon 8 mm in length. The grooves in the aluminum rod ran approx. 0.5 mm past the end of the substrate towards the fuel. The substrate was added with 150 mg of glycerol. The foil-clad tube, which was the same as in Example 1, surrounded part of the rear part of the fuel element. A void was left between the non-burning end of the fuel element and the substrate. A series of holes were cut through the foil-clad tube in this empty area to allow air flow. A similar smoking article was constructed with a pressed carbon fuel plug.

EXAMPLE 7

A smoking article was constructed as shown in fig. 4 with a carbonized cotton fiber fuel source. Four cotton strips were tightly braided together with cotton string to form a rope with a diameter of approx. 10.2 mm. This material was placed in a nitrogen atmosphere furnace heated to 950°C. It took approx. 1 1/2 hours and reach this temperature, which was then held for 1/2 hour. A 16 mm piece was cut from this pyrolyzed material and used as a fuel element. A 2 mm axial hole 16 was made through the element with a probe. The fuel element was inserted 2 mm into a 20 ml long foil-covered tube of the type described in example 1.

100 mg of Union Carbide PC-25 in granular form containing 60 mg of a 1:1 propylene glycol-glycerol mixture was placed in the foil-lined tube. A 5 mm long plug of tobacco, approx. 60 mg, was placed immediately behind the granular substrate in the foil-lined tube. A 48 mm long annular cellulose

acetate tube with an internal 4.5 mm I.D. polypropylene pipes were inserted approx. 3 mm in the foil-covered tube. A second foil-lined tube, 50 mm long, was inserted over the cellulose acetate tube until it rested against the 20 mm foil-lined tube. A 5 mm long cellulose acetate filter plug was inserted into the end of this second foil-lined tube. The total length was 84 mm. Upon ignition, this article of manufacture produced significant amounts of aerosol during the first six puffs with a tobacco flavor.

EXAMPLE 8

A smoking article was constructed as shown in fig. 5 with a 15 mm long fiber fuel element essentially as described in Example 7. The macrocapsule 52 was formed from a 15 mm long piece of 0.10 mm thick aluminum foil, which had been shrunk to a 12 mm long capsule. This macrocapsule was loosely filled with 100 mg of granulated PC-60, a carbon from Union Carbide, and 50 mg of mixed tobacco. The granular carbon was impregnated with 60 mg of a 1:1 mixture of propylene glycol and glycerol. The macrocapsule, fuel element, and mouthpiece were joined with an 85 mm long piece of regular cigarette paper.

EXAMPLE 9

A smoking article was constructed according to the embodiment of FIG. 6 with a 7 mm long pressed carbon fuel cell containing 90% PXC carbon and 10% SCMC. The elongated passage was 1.02 mm in diameter. This fuel plug was inserted into a 17 mm long aluminum foil lined tube so that 3 mm of the fuel element was inside the tube. An 8 mm diameter disc of 0.089 mm aluminum foil with a 1.24 mm diameter center hole was inserted into the other end of the tube and abuts the end of the fuel source.

Union Carbide PG-60 carbon was granulated and sieved to a particle size of -6 to +10 mesh. 80 mg of this material was used as substrate, 80 mg of a 1:1 mixture of glycerol and propylene glycol was placed on this substrate. Impregnated granules were inserted into the foil tube and rested against the foil disk at the end of the fuel source. 50 mg of the mixed tobacco was placed loosely against the substrate granulate. An additional foil disc with a 1.24 mm center hole was inserted into the foil tube at the mouth end of the tobacco. A long hollow cellulose acetate rod with a hollow polypropylene tube as described in Example 7 was inserted 3 mm into the foil-covered tube. A second foil-lined tube was inserted over the cellulose acetate rod toward the end of the foil-lined 17 mm tube.

This model emitted 11.0 mg of aerosol in the first three puffs when "smoked" under FTC conditions. Total aerosol release for nine puffs was 24.9 mg.

EXAMPLE 10

A smoking article with a fuel element and the substrate form

from fig. 7 was made using a 15 mm long annular pressed Carbon Fuel Element with an internal diameter of approx. 4 mm and an external diameter of approx. 8 mm. The fuel was made of 90% PCB-G activated carbon and 10% SCMC. The substrate was a 10 mm long piece formed from Union Carbide PC-25 carbon with an outside diameter of approx. 4 mm. The substrate coated with 55 mg of a 1:1 glycerol/propylene glycol mixture was inserted into the end of the fuel closer to the mouth end of the article. This fuel/substrate combination was inserted 7 mm into a 70 mm foil lined tube which had a short cellulose acetate filter at the mouth end. The length of the article was approx. 77 mm.

The article emitted significant amounts of aerosol in the first

three strokes, and throughout the lifetime of the fuel element.

Claims (5)

1. Smoking article comprising a combustible fuel element (10) and a physically separate aerosol-forming device (12) containing a substrate (20, 30, 38, 54, 76, 80) containing an aerosol-forming material, the aerosol-forming device being located longitudinally behind the fuel element, characterized in that the smoking article additionally contains a heat-conducting element (99, 50, 52, 66, 84, 87) which is designed and arranged to transfer heat from the fuel element (10) to the aerosol forming device (12) throughout the substantial burning time of the fuel element (10), and which is either in contact with or overlaps at least a part of the fuel element (10) and the aerosol generating device (12). 2. Smoking article according to claim 1, characterized in that the heat-conducting element consists of a container (50, 52, 66, 84, 87) which surrounds the aerosol-forming device (12) and allows passage of air and aerosol-forming material. 3. Smoking article according to claims 1 and 2, characterized in that the heat-conducting element (99) is at least partially located in the fuel element (10). 4. Smoking article according to claims 1-3, characterized in that the heat-conducting element (99, 50, 52, 66, 84, 87) is a metallic element. 5. Smoking article according to claims 1-4, characterized in that it further comprises a tobacco filling (28, 56, 78) in contact with the heat-conducting element (99, 50, 66, 84, 87).