NO172522B - 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 an elongated cigarette-type smoking article comprising a fuel element and a physically separate aerosol-forming device containing at least one aerosol-forming material.

Many smoking articles have been proposed over the years, particularly 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 an elastic insulating element surrounding at least part of the fuel element and comprising inorganic fibers and having a thickness of at least 0.5 mm, e.g. 1-2.5 mm.

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.

Part of the fuel element is provided with an enclosing insulating element such as a mantle of insulating fibers, the mantle being elastic and at least 0.5 mm thick, which reduces radial heat loss and helps to retain and direct heat from the fuel element towards the aerosol generating device. The insulation element passes over at least part of the fuel element and advantageously at least part of the aerosol

the formation device.

Because the preferred fuel element is relatively short, the hot, burning cone of fire is always close to the aerosol generating device, maximizing heat transfer thereto and maximizing the resulting aerosol production, particularly in embodiments equipped with a heat conducting element. The preferred use of a relatively short substrate or low mass carrier as an aerosol generating device close to the short fuel element also increases aerosol production by minimizing the heat loss effect of the substrate. 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 fire cone, which minimizes the possibility of thermal breakdown of the aerosol generator. Furthermore, the use of a carbonaceous fuel element that is substantially free of volatile organic matter eliminates the presence of significant pyrolysis or incomplete combustion products and eliminates the generation of significant sidestream smoke.

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 have 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 in connection with the invention, "aerosol" includes vapours, gases, particles and the like, both visible and invisible, and especially such components that the smoker experiences as "smoke-like" formed by the effect 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 here, 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 herein, 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 carbon and similar materials as well as materials which fuse during use such as low temperature grades of glass fibers. 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 and 2 are longitudinal sections of two embodiments of the invention;

The embodiments shown in fig. 1 and 2 includes a non-burning insulating jacket 86 around the fuel element 10 to isolate and concentrate the heat in the fuel element. These embodiments also help to reduce any risk of fire from the burning fire cone.

In the embodiment shown in fig. 1, both fuel element 10 and substrate 30 are located in an annular sheath or tube 86 of insulating fibers, such as ceramic (for example glass) fibers. Non-combustible carbon or graphite fibers can be used instead of ceramic fibers. The fuel element 10 is preferably an extruded carbon plug with a hole 16. In the illustrated embodiment, the ignition end 11 extends slightly beyond the edge of the jacket 86 to facilitate ignition. The substrate 30 is a solid porous carbon material, although other types of the substrate can be used. The substrate and rear portion of the fuel element is surrounded by a piece of aluminum foil 87. As illustrated, this jacketed fuel/substrate assembly is connected to a mouth end piece such as the elongated cellulose acetate tube 40 shown in the drawing, with a wrapper of plain cigarette paper 46. The sheath 86 extends to the mouth end of the substrate 30, but may replace the cellulose acetate rod 42.

In the embodiment shown in fig. 2, an aluminum macrocapsule 52 is used to surround a granular substrate 54 and tobacco 56. This macrocapsule is preferably placed completely inside the insulating jacket 86. In addition, the ignition end 11 of the fuel element 10 does not protrude past the front end of the jacket 86. Preferably the macrocapsule and the rear part of the fuel element are surrounded by a piece of aluminum foil in a similar way as shown in fig. 1. Alternatively, the aluminum foil 52 surrounding the substrate is only crimped at the mouth end. In such an embodiment, the rear end of the fuel element can be inserted into one end of the foil and a polypropylene tube can be threaded over or placed in connection with the mouth end of the foil. The whole unit is wrapped in fiberglass to a diameter like a regular cigarette.

After ignition of one of the aforementioned embodiments, the fuel element burns and provides the heat that is 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 regular 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 near the aerosol forming device becomes hot quickly, which significantly increases the heat transfer to the aerosol forming 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 draws 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 being bound by this 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 greatly increased by the hole or holes in the fuel element, is used primarily 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 believed to reduce the carbon combustion temperature, which is further believed 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 related 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>.

The preferred fuel elements used here are primarily formed from a carbonaceous material. Carbonaceous fuel elements are preferably from approx. 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 give minimal pyrolysis and incomplete combustion products. little or no, visible sidestream smoke, and minimal ash and has a high heat 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.

Furthermore, although not preferred, other fuel materials can be used such as tobacco, tobacco substitutes and the like, provided that they generate and conduct sufficient heat to the aerosol forming device to provide the desired amount of aerosol 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 can 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 pyrolyzed 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.

Although undesirable in most cases, carbonaceous fuel elements that 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 that require the use of a glow suppressant or other type of combustion modifier. Such combustion modifiers 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 ignitability. 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 are within 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 filter, fibers and mats, activated carbons and porous carbons such as PC-25 and PG-60 from Union Carbide as well as SGL carbon from Calgon.

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 located 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 mm, 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 one 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 components can be mixed with the substrate and distributed evenly through it before 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.

4 5 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 be burned. 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 generating device and the mouth end, such as in a separate substrate or chamber in the passage leading from the aerosol generating 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

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.

Insulating elements that can be used in the present invention generally comprise inorganic or organic fibers such as those made of glass, aluminum oxide, silicon dioxide, glassy materials, minerals, carbons, silicones, boron, organic polymers, cellulose materials and the like including mixtures of these materials. Insulating non-fibrous materials such as silica airgel, pearlite, glass and the like formed in mats, strips or other form can also be used. Preferred insulating elements are elastic to help simulate the feel of a regular cigarette. These materials act primarily as an insulating mortar, retaining and directing a significant portion of the heat generated by the fuel element towards the aerosol generating device. Because the insulating mantle gets hot near the burning fuel element to a certain extent, it can also conduct heat towards the aerosol generating device.

Commonly preferred insulation materials are ceramic fibers such as glass fibers. Two particularly preferred glass fibers are available from the Manning Paper Company of Troy, New York under the designations Manniglas 1000 and Manniglas 1200. Generally, the insulating fiber is packed over at least a portion of the fuel element and any other desired portion of the article to a final diameter from approx. 7 to 8 mm. Thus, the preferred thickness of the insulation layer is from approx. 0.5 mm to 2.5 mm, preferably from approx. 1 mm to 2 mm. If possible, the fiberglass materials have a low softening point, for example below approx. 650°C is preferred.

When the insulating device is fibrous, a barrier is preferably used at the mouth end of the article. Such a barrier comprises an annular element of high-density cellulose acetate web that abuts the insulation fiber and is sealed, preferably at the mouth end, with, for example, glue to block air flow through the web.

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 of the article's other elements. Preferred mouthpieces are the cellulose acetate tube used in the embodiments of figures 1 and 2.

The mouthpieces may contain an optional "filter11" tip, which is used to give the article the appearance of a regular 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 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 proponents of the Ames test, a significant dose-dependent response indicates the presence of mutagenic materials in the products being 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 regular 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 example which contributes to the understanding of the present invention. 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

A modified version of the smoking article of FIG. 2 was made as follows: A 9.5 mm long carbon fuel source with a 4.5 mm diameter and a 1 mm diameter longitudinal passage was extruded from a mixture of 10% SCMC, 5% potassium carbonate and 85% carbonized paper mixed with 10% water. The mixture had a dough-like consistency and was fed to an extruder. The extruded material was cut lengthwise after drying at 80°C overnight. The macrocapsule was made from a 22 mm long piece of 0.0089 mm thick aluminum formed into a cylinder with a 4.5 mm internal diameter. The macrocapsule was filled with (a) 70 mg of vermiculite containing 50 mg of a 1:1 mixture of propylene glycol and glycerol, and (b) 30 mg of burley tobacco to which 6% glycerol and 6% propylene glycol had been added. The fuel source and the macrocapsule were united by placing the fuel source approx. 2 mm into the end of the macrocapsule. A 35 mm long polypropylene tube with a 4.5 mm internal diameter was inserted into the other end of the macrocapsule. The fuel source, macrocapsule and polypropylene tube were thus united into a 65 mm long, 4.5 mm diameter segment. This segment was wrapped in several layers of Manninglas 1000 from Manning Paper Company until a circumference of 24.7 mm was reached. The device was then combined with a 5 mm long cellulose acetate filter and wrapped with cigarette paper. Smoking under FTC conditions, the article emitted 8 mg WTPM through the first three puffs; 7 mg WTPM through puffs 4-6; and 5 mg WTPM through puffs 7-9. Total aerosol release over the nine puffs was 20 mg. When the article was placed horizontally on a piece of tissue paper, it neither ignited nor burned the tissue paper.

Claims (7)

1. Elongated cigarette-type smoking article comprising a fuel element (10) and a physically separate aerosol-forming device containing at least one aerosol-forming material, characterized in that an elastic insulation element (86) circumscribes at least part of the fuel element (10) and comprises inorganic fibers and has a thickness of at least 0.5 mm, e.g. 1-2.5 mm. 2. Smoking article according to claim 1, characterized in that the inorganic fibers are selected from those which fuse together during the burning of the fuel element. 3. Smoking article according to claim 1 or 2, characterized in that the insulation element (86) is enveloped by a paper overwrap (46). 4. Smoking article according to claims 1-3, characterized in that the insulation element (86) is non-combustible. 5. Smoking article according to claims 1-4, characterized in that the insulation element (86) additionally surrounds at least part of the aerosol-forming device. 6. Smoking article according to claims 1-5, characterized in that the insulation element (86) comprises a low-temperature quality of glass fibres. 7. Smoking article according to claims 1-6, characterized in that the insulation element (86) comprises glass fibers with a softening point below approx. 650°C.