DE3587920T2 - Smoking articles. - 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 having a front and a rear end, which comprises a fuel element having an ignitable end and physically separate aerosol generating means, the latter comprising at least one aerosol forming material and disposed between the ignitable end of the fuel element and said rear end. In particular, the present invention relates to a smoking article of the type which generates an aerosol which is similar to tobacco smoke and contains no more than a minimal amount of incompletely burned combustion or pyrolysis products.

In recent years, particularly during the last 20 to 30 years, a variety of smoking articles have been proposed, but none of these products has been successful in establishing itself on the market.

US-A-4 340 072 describes a proposed cigarette-like smoking article which comprises a rod-like fuel element arranged one behind the other with a wrapper made of cigarette paper and a central axial passage, aerosol generating means defined by a chamber and a short filter tip. The total length of the smoking article is 70 mm and its diameter is 7 mm. The fuel element is a made of reconstituted tobacco and/or tobacco substitute, e.g. a mixture of carbon and a binder (NaCMC), molded or extruded, and the front end of its axial passage can be closed with a plug made of the same material, which serves the purpose of closing the central axial passage of the fuel element and thus assisting in uniform ignition of the smoking article. The aerosol generating means chamber contains an inhalation material which, when contacted with hot gases generated by the burning fuel element and drawn through the axial passage of the fuel element and through the aerosol generating means chamber, purports to form an aerosol for inhalation by the smoker. According to the drawings associated with US-A-4 340 072, the length of the rod-like fuel element is about 73% of the total length of the cigarette-like smoking article, that is to say about 51 mm.

EP-A-0 117 355 describes a proposed cigarette-like smoking article which comprises a carbon heat source with an axial passage and a separate aroma generator (taste and odour generator). The formation of the heat source (page 2, line 23 to page 7, line 14) is carried out by pyrolysing a preformed, tubular lignocellulosic pulp material of, for example, 90 mm or 65 mm length (see Comparative Example 1 or Example 4) under predetermined conditions, followed by at least one additional predetermined process step. The alleged aroma generator (page 8, lines 8 to 27) comprises a substrate, such as tobacco, aluminium oxide etc., located near the mouth end, which is impregnated with or inherently contains at least one heat-releasable flavouring agent. The aroma generator may also contain a flavoured foamed core inside the heat source. A conventional filter may be placed behind the aroma generator. The alleged formation of an aerosol during use is described from page 8, line 28 to page 9, line 8. During pyrolysis, the tubular lignin-containing pulp material experiences a maximum shrinkage of its dimensions of 37.5% (see page 12, lines 3 and 4), so that a carbon heat source having a length of more than 40 mm is obtained from a tubular lignin-containing pulp material having a length of 65 mm.

Despite decades of interest and effort, there is currently no smoking product on the market that can provide the benefits and advantages associated with traditional cigarette smoking without simultaneously releasing significant amounts of incompletely burned combustion or pyrolysis products.

The present invention is based on the object of creating a smoking article of the type which has a fuel element and a separate aerosol generator and provides a higher level of efficiency when smoking.

This object is achieved according to the invention by creating a smoking article as defined above, which has an elastic insulating element which encloses at least part of the fuel element, contains inorganic fibers and is at least 0.5 mm thick, as well as a casing for the insulating element.

In such a smoking article, the heat generated by the fuel element during smoking is used more effectively to form an aerosol that resembles the smoke from a conventional smoking article.

The smoking article according to the invention is capable of forming substantial amounts of aerosol both at the beginning and during the useful life of the product, without any significant thermal decomposition of the aerosol forming agent, without the occurrence of substantial amounts of pyrolysis or incompletely burned combustion products and preferably without substantial amounts of sidestream smoke. Smoking article according to the present invention are able to convey to the user the perceptions and benefits of cigarette smoking without burning tobacco.

The preferred fuel element is less than about 30 mm, more preferably less than 15 mm long, has a density of at least 0.5 g/cm3 and has one or more longitudinal passages. Advantageously, the aerosol generating means comprises a heat resistant substrate including one or more aerosol forming substances. Preferably, the heat exchange between the fuel and the aerosol generator is effected by means of a heat conducting element, for example a metal foil, which enables effective heat conduction or transfer from the burning fuel element to the aerosol generating means. Preferably, this heat conducting element is in contact with at least part of the respective peripheral surface of the fuel element and the aerosol generating means. Furthermore, at least part of the fuel element is provided with a peripheral insulating element, such as a sleeve made of insulating fibers, said sleeve being elastic and at least 0.5 mm thick, which leads to a reduction in radial heat loss and helps to retain and direct the heat from the fuel element to the aerosol generating means. The insulating element preferably envelops at least part of the fuel element and advantageously at least part of the aerosol generating means.

Since the preferred fuel element is relatively short, the hot, burning ember cone is always close to the aerosol generating means, thereby maximizing heat transfer to the aerosol generating means and the resulting aerosol formation, particularly in embodiments equipped with a heat-conducting element. The preferred use of a relatively short and low-mass substrate or carrier as the aerosol generating means very close to the short fuel element further increases aerosol formation by reducing the effect of the substrate as a heat sink to a Since the aerosol forming substance and the fuel element are physically separated, the aerosol forming substance is exposed to temperatures substantially lower than those prevailing in the burning ember cone, thereby minimizing the possibility of thermal decomposition of the aerosol forming substance. Furthermore, the particularly preferred use of a carbon fuel element which is substantially free of volatile organic components prevents the occurrence of significant amounts of pyrolysis or incompletely burned combustion products and the formation of significant amounts of sidestream smoke.

The smoking article according to the invention is typically provided with a mouthpiece which has means, such as a longitudinally extending passage, through which the volatile substances generated by the aerosol generating means are delivered to the user. Advantageously, the smoking article has the same overall dimensions as a conventional cigarette; accordingly, the mouthpiece and the aerosol delivery means typically extend over more than half the length of the smoking article. Alternatively, the fuel element and the aerosol generating means can be manufactured without an integrated mouthpiece or aerosol delivery means for use in conjunction with a separate mouthpiece for single or multiple use.

The smoking article of the present invention may also contain a tobacco filling or plug to impart a tobacco flavor to the aerosol. Preferably, the tobacco is placed at the mouth end of the aerosol generating means; however, it may also be mixed with the carrier of the aerosol-forming substance. Aromatics (flavors and odors) may also be included in the smoking article to flavor the aerosol delivered to the user.

Preferred embodiments of the invention are capable of delivering at least 0.6 mg of aerosol, measured as total wet particles, in the first 3 puffs under FTC smoking conditions. (FTC smoking conditions consist of puffs of 2 seconds duration (35 ml total volume) separated by 58 seconds of smoldering.) Even more preferred embodiments of the invention are capable of delivering 1.5 mg or more of aerosol in the first 3 puffs. The most preferred embodiments of the present invention are capable of delivering 3 mg or more of aerosol in the first 3 puffs under FTC smoking conditions. Furthermore, preferred embodiments of the invention deliver on average a total wet particle amount of at least about 0.8 mg per puff under FTC smoking conditions over at least about 6 puffs, preferably over at least about 10 puffs.

Furthermore, the smoking article of the present invention is capable of providing a chemically simple aerosol consisting essentially of carbon oxides, air and water, and which may carry any desired flavorings or other desired volatiles, as well as trace amounts of other materials. Preferably, the aerosol does not exhibit significant mutagenic activity according to the Ames test to be described. Furthermore, the smoking article may be designed to be virtually ashless, so that the user does not have to remove ash during use.

In the present description and solely for the purposes of the present application, the definition of the term "aerosol" includes both visible and invisible vapors, gases, particles and the like, in particular those components which are perceived by the user as "smoke-like" and which are generated by the action of the heat of the burning fuel element on the substances contained in the aerosol generating means or another part of the smoking article. According to this definition, the term "aerosol" also includes volatile flavorings and/or pharmacologically or physiologically active ingredients, regardless of whether they produce visible aerosol or not.

In the present specification, the term "conductive heat exchange" means such a physical arrangement of the aerosol generating means and the fuel element in which heat is transferred by conduction from the burning fuel element to the aerosol generating means substantially throughout the burning time of the fuel element. Conductive heat exchange can be achieved by arranging the aerosol generating means so that it is in contact with the fuel element and is located very close to the burning part of the fuel element and/or by using a conductive element which transfers heat from the burning fuel to the aerosol generating means. Preferably, both methods are used to achieve conductive heat transfer.

In this description, the term "carbon(-)" means "containing predominantly carbon".

In the present specification, the term "insulating materials" refers to all materials which act primarily as insulators. Preferably, these materials do not burn in use, but they may include, for example, slow-burning carbons and similar substances and materials which melt in use, such as low-temperature types of glass fiber. The insulators have a thermal conductivity in gcal/(s) (cm²) (ºC/cm) of less than about 0.05, preferably less than about 0.02, most preferably less than about 0.005. See Hackh's Chemical Dictionary, 34 (4th edition 1969) and Lange's Handbook of Chemistry, 10, 272-274 (11th edition 1973).

It is proposed to use a fuel element through which a plurality of passages extending in the longitudinal direction lead.

A preferred embodiment of the smoking article according to the invention comprises a heat-conducting element which is in contact with both the fuel element and the aerosol generating means. The heat-conducting element is preferably metallic. It is further proposed to use a metal foil as the relevant metallic element, which encloses at least part of both the fuel element and the aerosol generating means. For a smoking article of this type, it is proposed to use a metallic element which encloses a substrate carrying the aerosol-forming material. In an alternative embodiment, the metallic element is a metallic rod which is at least partially embedded in both the fuel element and the aerosol generating means.

It may be advantageous to arrange the aerosol generating means so that they are at least partially contained in a cavity in the fuel element.

Preferably, the aerosol generating means comprises a porous, non-particulate substrate having a longitudinal passageway over at least a portion of its length.

In a preferred embodiment, the aerosol generating means comprise a substrate loaded with an aerosol generator in an amount of about 35 mg to 85 mg. Preferably, under FTC fume conditions, at least about 15% by weight of the aerosol generator is delivered as a total amount of wet particles.

A preferred embodiment of the smoking article according to the invention comprises a tobacco charge between the mouth end of the fuel element and the mouth end of the smoking article.

Preferred embodiments of the smoking article according to the invention are designed such that the fuel element produces essentially no visible sidestream smoke during smoldering.

A preferred embodiment of an elongated smoking article according to the invention comprises a fuel element having a length of less than 30 mm, physically separate aerosol generating means including a carrier substance carrying an aerosol-forming material, means for transferring heat from the fuel element to the aerosol generating means by conduction, and an insulating element enclosing at least a portion of the fuel element. Preferably, the heat-conducting means comprises a heat-conducting element in contact with both the fuel element and the aerosol generating means; more preferably, the heat-conducting element encloses the carrier of the aerosol-forming material.

Further advantageous features are the subject of the appended claims 2 to 89.

The smoking article of the present invention is explained in more detail in the attached drawings and the following detailed description of the invention.

BRIEF DESCRIPTION OF THE CHARACTERS

Figures 1 and 2 show two embodiments of the invention in longitudinal section.

The embodiment of the invention shown in Fig. 1, which preferably has the diameter of a conventional cigarette, comprises a short, combustible carbon fuel element 10 and an aerosol generating means 30 abutting thereon. The fuel element 10 may comprise a "soldering tube carbon", ie carbonized wood, a pressed or extruded carbon rod or plug, or another carbon fuel element and is provided with one or more longitudinally extending holes 16.

In this embodiment, the aerosol generating means 30 comprises a heat-resistant, conductive carbon substrate, such as a plug of porous carbon impregnated with one or more aerosol-forming substances. This substrate may optionally be provided with an axial passage.

The ignitable end 11 of the fuel element 10 may be tapered to improve ignitability.

The embodiments shown in Figures 1 and 2 include a non-combustible insulating sleeve 86 around the fuel element 10 which serves to insulate and concentrate heat within the fuel element. These embodiments also help to reduce any fire-causing potential of the burning ember.

In the embodiment shown in Figure 1, both the fuel element 10 and the substrate 30 are contained within an annular sleeve or tube 86 of insulating fibers such as ceramic fibers (e.g., glass fibers). Non-burning carbon or graphite fibers may be used in place of the ceramic fibers. The fuel element 10 is preferably an extruded carbon plug having a hole 16. In the embodiment shown, the ignition end 11 extends slightly beyond the edge of the sleeve 86 to facilitate ignition. The substrate 30 is a solid, porous carbon material, but other types of support materials may be used. The substrate and the rear portion of the fuel element are enclosed by a piece of aluminum foil 87. As shown, this wrapped fuel/substrate unit is enclosed by a wrapper of conventional cigarette paper 46 having a mouth end piece such as the elongated one shown in the figure. Cellulose acetate tube 40. The sleeve 86 extends to the mouth end of the substrate 30.

The tube 40 further forms an aerosol delivery passage 26 between the aerosol generating means 30 and the mouth end 15 of the smoking article.

The smoking article may optionally contain a quantity or plug of tobacco to impart aroma (smell or taste) to the aerosol. This tobacco charge may be disposed at the mouth end of the aerosol generating means 30 or in the passage 26 spaced from the aerosol generating means 30.

The tube 40 comprises an annular region 42 of cellulose acetate rod material which encloses an optional plastic tube 44, e.g. of polypropylene. As shown in Fig. 1, the sleeve 86 extends to the mouth end of the substrate 30, but it can also replace the cellulose acetate rod 42. At the mouth end 15 of the tube 44 is a low efficiency cellulose acetate filter plug 45.

In the embodiment according to Fig. 2, an aluminum macrocapsule 52 is used, which surrounds a granular substrate 54 and tobacco 56. This macrocapsule is preferably arranged completely inside the insulating sleeve 86. In addition, the end 11 of the fuel element 10 to be ignited does not protrude beyond the front end of the sleeve 86. Preferably, the macrocapsule and the rear part of the fuel element are surrounded by a piece of aluminum foil.

Alternatively, the aluminum foil 52 surrounding the substrate is bent only 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 arranged over or adjacent to the mouth end of the foil. The complete arrangement is covered with a glass fiber sheath to the diameter of a conventional cigarette.

The granular substrate 54 may be a granular, heat-resistant carbon. The capsule 52 is bent at its ends to surround the material 54, 56 and to inhibit migration of the aerosol generator. The fuel-side bent end preferably abuts against the rear end of the fuel element to allow heat transfer by conduction. A void formed by the front end of the capsule also helps to inhibit migration of the aerosol generator toward the fuel. Longitudinal passages are provided in the bent ends to allow passage of air and the aerosol generator substance. The capsule 52 and the fuel element 10 may be joined together using a conventional cigarette paper, a perforated ceramic paper or a foil strip. When using cigarette paper, a strip near the rear end of the fuel element should be printed or treated with sodium silicate or other known substances that cause the paper to extinguish.

In all of the above embodiments, once lit, the fuel element burns and generates the heat used to volatilize the aerosol-forming substance or substances present in the aerosol generating means. Similar to the smoke from a conventional cigarette, these volatiles are then drawn towards the mouth end, particularly when drawn, and into the user's mouth.

Since the fuel element is preferably relatively short, the hot burning ember cone is always close to the aerosol generating body, thereby maximizing heat transfer to the aerosol generating means and the resulting aerosol generation, particularly when the preferred heat-conducting element is used. In addition, the preferred insulating element helps to direct heat to the central core of the smoking article, thereby increasing the heat transfer to the aerosol-forming substance.

Since the aerosol-forming substance is physically separated from the fuel element, it is exposed to temperatures much lower than those prevailing in the burning ember cone. This minimizes the possibility of thermal decomposition of the aerosol-forming substance. It also results in aerosol being generated during drawing but not, or hardly, during smoldering. In addition, the use of the preferred carbon fuel element and physically separated aerosol-generating means precludes the occurrence of pyrolysis or incompletely burned combustion products in significant quantities and the formation of sidestream smoke in significant quantities.

Due to the small size and burning characteristics of the carbon fuel element preferably used in the present invention, the fuel element typically begins to burn over substantially its entire free length within a few puffs. Thus, the portion of the fuel element adjacent to the aerosol generating means quickly becomes hot, thereby significantly increasing heat transfer to the aerosol generating means, particularly during the first and middle puffs. Since the preferred fuel element is short, there is never a long section of non-burning fuel to act as a heat sink, as was common in previous smoking articles using thermal aerosol generation. Heat transfer, and hence aerosol delivery, is also increased by providing holes through the fuel through which hot air is drawn to the aerosol generator, particularly during the puff.

In the preferred embodiments of the invention, the short carbon fuel element, the heat-conducting element, the insulating means and the passages in the fuel interact with the aerosol generator to create a system that is capable of generating significant amounts of aerosol with practically every puff. The fact that the aerosol generator is located in the immediate vicinity of the glowing cone after a few puffs, in conjunction with the insulating materials, results in a high heat release both when puffing and during the relatively long glowing times between puffs.

Without wishing to be bound by theory, it is believed that the aerosol generating means is maintained at a relatively high temperature between draws and that the additional heat release during draws, which is greatly enhanced by the hole or holes in the fuel element, is used primarily to vaporize the aerosol forming substance. This increased heat transfer results in more efficient use of the available fuel energy, reduces the required fuel demand, and promotes early aerosol release. It is also believed that the conductive heat transfer utilized in the present invention reduces the combustion temperature of the carbon fuel, which is further believed to lower the CO/CO2 ratio of the combustion products produced by the fuel. See, for example, G. Hagg, General Inorganic Chemistry, p. 592 (John Wiley & Sons, 1969).

It is also possible to influence the combustion properties of the fuel source by selecting the appropriate fuel element, insulating sleeve, paper wrapper and heat-conducting means. This provides the opportunity to influence the heat transfer to the aerosol generator, which in turn results in a change in the number of puffs and/or the amount of aerosol delivered to the user.

Generally, the combustible fuel elements that can be used in the practice of the present invention are less than about 30 mm in length. Advantageously, the fuel element has a length of about 20 mm or less, preferably about 15 mm or less. Advantageously, the fuel element has a diameter between about 3 and 8 mm, preferably about 4 to 5 mm. The density of the fuel elements used in this specification ranged from about 0.5 g/cm³ to about 1.5 g/cm³. Preferably, the density is greater than 0.7 g/cm³, more preferably greater than 0.8 g/cm³. Preferably, the fuel has one or more longitudinally extending holes, such as holes 16 in Figs. 1 and 2. These holes impart porosity and enhance early heat transfer to the substrate by increasing the amount of hot gases reaching the substrate.

The preferred fuel elements used herein are comprised primarily of a carbon material. Carbon fuel elements preferably have a length of about 5 to 15 mm, more preferably about 8 to 12 mm. Carbon fuel elements having these characteristics provide sufficient fuel for at least about 7 to 10 puffs, the normal number of puffs typically achieved when smoking a conventional cigarette under FTC smoking conditions.

Preferably, the carbon content of such a fuel element is at least 60-70 weight percent, most preferably at least about 80 weight percent or more. Excellent results have been achieved with fuel elements having a carbon content greater than about 85 weight percent. High carbon fuels are preferred because they produce minimal amounts of pyrolysis or incompletely burned combustion products, produce little or no visible sidestream smoke, have minimal ash production, and have high heat capacity. However, fuel elements having lower carbon contents, e.g., about 50-65 weight percent, are also within the scope of this invention, particularly when a non-burning inert filler is used.

Other, although not preferred, fuels may also be used, such as tobacco, tobacco substitutes and the like, provided they can generate and transfer sufficient heat to the aerosol generating means to produce the desired level of aerosol from the aerosol forming material, as previously explained. The fuel used should have a density of greater than about 0.5 g/cm³, preferably greater than about 0.7 g/cm³, which corresponds to higher densities than those typically used in conventional smoking articles. When such other materials are used, it is highly desirable to add carbon to the fuel, preferably in an amount of at least about 20-40 wt.%, more preferably at least about 50 wt.%, and most preferably at least about 65-70 wt.%, with the balance being made up of the remaining fuel components, including binders, combustion-modifying additives, moisture, etc.

The carbon materials used with or as the preferred fuel can be derived from virtually any of the numerous carbon sources known in the art. Preferably, the carbon material is derived by pyrolysis or carbonization of cellulosic material such as wood, cotton, rayon, tobacco, coconut, paper and the like, but carbon material obtained from other sources can also be used.

In most cases, the carbon fuel element should be capable of being ignited using a conventional cigarette lighter without the aid of an oxidizer. Burning characteristics of this type can generally be achieved with cellulosic material which has been pyrolyzed at temperatures between about 400°C to about 1000°C, preferably between about 500°C to about 950°C, in an inert atmosphere or in a vacuum. The pyrolysis time is not considered critical as long as the temperature in the core of the pyrolyzed mass has reached the aforementioned temperature range for a period of at least several minutes. However, it is assumed that slow pyrolysis, with a gradual increase in temperature over several hours, will produce a more uniform material with a higher carbon yield.

Although undesirable in most cases, the scope of the present invention also includes carbon fuel elements that require the addition of an oxidizer to ignite them using a cigarette lighter, as well as carbon materials that require the use of a glow retardant or other type of burn-modifying additive. Such burn-modifying additives are disclosed in numerous patents and publications and are known to those skilled in the art.

The carbon fuel elements most preferred in the practice of the invention are substantially free of volatile organic materials. This means that the fuel element is not intentionally impregnated or mixed with substantial amounts of volatile organic substances, such as volatile aerosol-forming or flavoring agents, which could decompose in the burning fuel. However, small amounts of water that is naturally adsorbed by the fuel may be present therein. Similarly, small amounts of aerosol-forming substances may migrate from the aerosol-generating agents and thus also be present in the fuel element.

A preferred carbon fuel element is a pressed or extruded carbon mass made from carbon and a binder by conventional pressing or extrusion processes. 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 pressing and/or extrusion are made from pyrolyzed cotton or pyrolyzed papers.

The binding agents suitable for the production of such a fuel element are known in the specialist world. A preferred binding agent is sodium carboxymethylcellulose (NaCMC), which - as preferred - can be used alone or in combination with other substances, such as sodium chloride, vermiculite, bentonite, calcium carbonate and the like. Other suitable binding agents are, for example, rubber substances such as guar gum and other cellulose derivatives such as methylcellulose and carboxymethylcellulose (CMC).

The binder concentration can be within a wide range. Preferably, the binder content is limited in order to reduce the binder's contribution to undesirable combustion products to a minimum. On the other hand, sufficient binder must be added to hold the fuel element together during manufacture and use. The amount used therefore depends on the cohesiveness of the carbon in the fuel element.

If desired, the above fuel elements can be pyrolyzed after formation, for example for two hours at about 650ºC, to convert the binder into carbon, obtaining a fuel element consisting of practically 100% carbon.

The fuel elements used in the present invention may also contain one or more additives to improve fire, such as up to about 5% by weight of sodium chloride to improve smoldering properties and as a smoldering retarder. Up to about 5%, preferably 1 to 2% by weight of potassium carbonate may also be added to improve ignitability. Additives to improve physical properties may also be used, for example clays such as kaolin, serpentine, attapulgite and the like.

Another carbon fuel element is a carbon fiber fuel which can be prepared by carbonizing a fibrous feedstock such as cotton, rayon, paper, polyacrylonitrile and the like. Generally, pyrolysis in the range of about 650°C to 1000°C, preferably at about 950°C for about 30 minutes in an inert atmosphere or under vacuum is sufficient to form a suitable carbon fiber with good burning properties. Combustion modifying additives can also be added to these fibrous fuels.

The aerosol generating means used in the practice of the invention are arranged physically separate from the fuel element. Physically separate means that the substrate, container or chamber containing the aerosol forming substances are not mixed with or form part of the burning fuel element. As already explained, this arrangement helps to reduce or eliminate thermal decomposition of the aerosol forming substance and the occurrence of sidestream smoke. Although the aerosol generating means are not part of the fuel, they are in a conductive heat exchange with the fuel element and are preferably arranged so that they abut or adjoin the fuel element.

Preferably, the aerosol generating means comprise one or more heat-resistant materials carrying one or more aerosol forming substances. For the purposes of the present specification, a heat-resistant material is a material which is capable of withstanding the high temperatures prevailing in the vicinity of the fuel, e.g. 400°C-600°C, without decomposing or burning. It is believed that the use of such a material helps to maintain the simple "smoke" chemical composition of the aerosol, as evidenced by the absence of Ames activity in the preferred embodiments. Other, although not preferred, aerosol generating means are also possible, such as for example, microcapsules or solid aerosol-forming substances which burst due to thermal stress, are within the scope of the invention, provided that they are capable of releasing sufficient aerosol-forming vapours such that a satisfactory tobacco smoke-like image is obtained.

The heat-resistant materials suitable as a substrate or carrier for the aerosol-forming substance are well known in the specialist world. Such substances should be porous and must be able to retain an aerosol-forming compound when not in use and to release a vapor, which is a potential aerosol generator, when heated by the fuel element.

Suitable heat-resistant materials include, for example, heat-resistant adsorbent carbons, such as porous carbons, graphite, activated carbon or non-activated carbons and the like. Other suitable materials include, for example, inorganic solids, such as ceramics, glass, aluminum oxide, vermiculite, clays, such as bentonite, and the like. Currently preferred carrier materials are carbon felts, fibers and mats, activated carbons and porous carbons, such as the PC-25 and PG-60 grades sold by Union Carbide, and the SGL carbon sold by Calgon.

Depending on the type of specific aerosol generating agents used here, their composition and design can generally be selected as particulate, fibrous, as a porous body, as a solid body with one or more axially extending passages and the like. Substrates, in particular particulate, can be housed in a container preferably formed from a metal foil.

The aerosol generating means used in this invention are typically located no more than about 60 mm, preferably no more than 30 mm, most preferably no more than 15 mm from the end of the fuel element to be ignited.

The length of the aerosol generator may range 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. When using a non-particulate substrate, the substrate may be provided with one or more holes to increase the surface area of the substrate and increase the amount of air and heat transfer.

The aerosol-forming substance(s) used in the invention must be capable of forming an aerosol at the temperatures generated in the aerosol generating means when heated by the burning fuel element. Preferably, such substances will consist of carbon, hydrogen and oxygen, but they may also contain other substances. The aerosol-forming substances may be solid, semi-solid or liquid. The boiling point of the substance and/or mixture of substances may be in a range up to approximately 500°C. Substances having these properties include, for example, polyhydric alcohols such as glycerol and propylene glycol, and aliphatic esters of mono-, di- or polycarboxylic acids such as methyl stearate, dodecanedioate, dimethyltetradodecanedioate and others.

Preferably, the aerosol forming substances comprise a mixture of a high boiling substance with a low vapor pressure and a low boiling substance with a high vapor pressure. In this way, the low boiling substance can provide most of the initial aerosol in the first few puffs, while as temperatures in the aerosol generator increase, the aerosol comes predominantly from the high boiling substance.

The preferred aerosol-forming substances are polyhydric alcohols or mixtures of polyhydric alcohols. The particularly preferred aerosol formers include glycerol, propylene glycol, triethylene glycol or mixtures thereof.

The aerosol-forming substance may be dispersed on or in the aerosol generating means in a concentration sufficient to penetrate or cover the substrate, carrier or container. For example, the aerosol-forming substance may be applied undiluted or in a dilute solution by dipping, spraying, vapor deposition or similar techniques. Prior to molding, solid aerosol-forming components may be mixed into the substrate and evenly distributed throughout it.

While the loading of the aerosol-forming substance varies from carrier to carrier and from aerosol-forming substance to aerosol-forming substance, for liquid aerosol-forming substances the amount can typically 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 of the aerosol-forming agent applied to the aerosol-generating means as possible should be delivered to the user as total wet particulate matter (WTPM). Preferably, over about 2% by weight, more preferably over about 15% by weight, and most preferably over about 20% by weight of the aerosol-forming agent applied to the aerosol-generating means is delivered to the user as WTPM.

The aerosol generating means may further contain one or more volatile flavoring agents, such as menthol, vanillin, artificial coffee, tobacco extracts, nicotine, caffeine, alcohols and other substances that impart flavor to the aerosol. The aerosol generating means may also contain other desirable volatile solid or liquid substances.

As already stated, the smoking article of the present invention may also contain a tobacco charge or plug to impart a tobacco flavor to the aerosol. Preferably, the tobacco is placed at the mouth end of the aerosol generating means; however, it may also be mixed with the carrier for the aerosol-forming substance. Flavorings may also be included in the smoking article to flavor the aerosol delivered to the user.

When a tobacco charge is used, hot vapors are passed through the tobacco layer to extract and vaporize the volatile components of the tobacco without the need to burn the tobacco. This provides the user of this smoking article with an aerosol that has the properties and aroma of natural tobacco, but without the combustion products produced by a conventional cigarette.

Alternatively, these optional substances may be located between the aerosol generating means and the mouth end, for example on a separate substrate or in a separate chamber in the passage leading from the aerosol generating means to the mouth end or in the optional tobacco charge. If desired, these volatile substances may be used to replace all or part of the aerosol generating substance so that the smoking article delivers a non-aerosolized flavor or other substance to the user.

Smoking articles of the type disclosed in the present description may also be used as drug delivery articles or modified for use as such to deliver volatile pharmacologically or physiologically active substances such as ephedrine, metaproterenol, terbutaline or the like.

The heat-conducting element preferably used in the practice of the present invention is typically a metal foil, such as aluminum foil, which may range in thickness from less than about 0.01 mm to about 0.1 mm or more. The thickness and/or type of conductive material may be varied to achieve virtually any desired level of heat exchange. As shown in the illustrated embodiments, the heat-conducting element is preferably arranged to form part of the fuel element and the aerosol generating means. contacted or overlapped, and may form the container that encloses the aerosol-forming substance.

The insulating elements suitable for use in the invention typically include inorganic or organic fibers, for example those made of glass, aluminum oxide, silicon dioxide, glassy materials, mineral wool, carbon, silicon, boron, organic polymers, cellulose derivatives and the like, including mixtures thereof. Non-fibrous insulating materials such as silica aerogel, perlite, glass and the like in mats, strips or other forms may also be used. The preferred insulating elements are elastic to provide the feel of a conventional cigarette. These materials function primarily as an insulating sleeve, retaining a substantial portion of the heat generated by the burning fuel element and directing it to the aerosol generating means. Since the insulating sleeve heats up to a limited extent in the vicinity of the burning fuel element, it can also conduct heat to the aerosol generating means.

Currently preferred insulating materials include ceramic fibers, such as glass fibers. Two particularly preferred glass fibers are available from the Manning Paper Company of Troy, New York, under the designation Manniglas 1000 and Manniglas 1200. Typically, the insulating fiber will envelop at least a portion of the fuel element and any other portion of the smoking article to a final diameter of about 7 to 8 mm. Thus, the preferred insulating layer is from about 0.5 mm to 2.5 mm thick, more preferably from about 1 mm to 2 mm. Where possible, it is preferred to use glass fibers with a low melting point, e.g., below about 650°C.

When using a fibrous insulating material, a blocking means is preferably provided at the mouth end of the smoking article. Such a blocking means comprises, for example, an annular element made of a high-density cellulose acetate strand, which abuts the fibrous insulating material and is preferably provided at the mouth end, for example with adhesive, to prevent air from flowing through the strand.

In most embodiments of the invention, the fuel/aerosol generating agent combination is attached to a mouthpiece, such as a foil-lined paper or cellulose acetate/plastic tube as shown in the figures, but a separate mouthpiece may be provided, e.g. in the form of a cigarette holder. This element of the smoking article forms the passageway which directs the vaporous aerosol-forming substance into the user's mouth. Due to its length, which is preferably about 50 to 60 mm or more, it also keeps the hot cone of embers away from the user's mouth and fingers.

Suitable mouthpieces should be inert with respect to the aerosol forming substances, have a water or liquid tight inner layer, cause minimal aerosol loss by condensation or filtration and be able to withstand the temperature at the interface with the other elements of the smoking article. Preferred mouthpieces comprise the cellulose acetate tube used in the embodiments of Figures 1 and 2. Other suitable mouthpieces are known to those skilled in the art.

For example, the mouthpieces of the invention may include an optional "filter" tip used to give the smoking article the appearance of a conventional filter cigarette. Such filters include low density cellulose acetate filters and hollow or baffled plastic filters such as polypropylene filters. The smoking article may also be wrapped in cigarette paper along all or any portion of its length.

The aerosol produced by the preferred smoking articles of the present invention is chemically simple and consists essentially of air, carbon oxides, the desired flavorings or other desirable volatiles, water, and trace amounts of other substances. The total wet particulate matter (WTPM) produced by the preferred smoking articles of the present invention does not exhibit mutagenic activity according to the Ames test procedure, that is, there is no significant dose-response relationship between the WTPM of the present invention and the number of revertants encountered by such products when exposed to standard test microorganisms. According to the proponents of the Ames test, a significant dose-related response indicates the presence of mutagenic agents in the products tested. See Ames et al., Mut. Res., 31:347-364 (1975); Nagas et al., Mut. Res., 42:335 (1977).

Another advantage of the preferred embodiments of the present invention is that relatively little ash is produced during use as compared to a conventional cigarette. The preferred carbon fuel source is substantially converted to carbon oxides during combustion, producing relatively little ash, thereby eliminating the need to remove ash during use of the smoking article.

The smoking article of the present invention is explained in more detail with reference to the following example, which serves to better understand the present invention, without the present invention being limited thereto. The percentages mentioned herein are to be understood as percentages by weight, unless otherwise stated. All temperatures are expressed in degrees Celsius and are to be understood as unadjusted. In all cases, the smoking articles have a diameter of approximately 7 to 8 mm, the diameter of a conventional cigarette.

EXAMPLE

A modified version of the smoking article of Fig. 2 was prepared as follows: A 9.5 mm long carbon fuel source with a diameter of 4.5 mm and a longitudinal passage of 1 mm diameter was extruded from a mixture of 10% NaCMC, 5% potassium carbonate and 85% carbonized paper mixed with 10% water. The mixture had a dough-like consistency and was fed into an extruder. The extruded material was dried overnight at 80ºC and then cut to length. The macrocapsule was formed from a piece of aluminum 22 mm long and 0.0089 mm thick formed into a cylinder with an inner diameter of 4.5 mm. 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 macrocapsule were connected by inserting the fuel source approximately 2 mm into the end of the macrocapsule. A 35 mm long polypropylene tube with an inner diameter of 4.5 mm was inserted into the other end of the macrocapsule. In this way, the fuel source, macrocapsule and polypropylene tube were joined together to form a 65 mm long section with a diameter of 4.5 mm. This section was wrapped with several layers of Manniglas 1000 from the Manning Paper Company until a circumference of 24.7 mm was achieved. The unit was then combined with a 5 mm long cellulose acetate filter and wrapped in cigarette paper. When smoked under FTC conditions, the smoking device delivered 8 mg WTPM in the first three puffs, 7 mg WTPM from puffs 4-6, and 5 mg WTPM from puffs 7-9. A total of 20 mg of aerosol was delivered over the 9 puffs. When placed horizontally on a piece of tissue paper, the paper did not ignite or even become scorched.

Claims (89)

1. Smoking article with a front and a rear end, which comprises: (a) a fuel element (10) having an end (11) to be ignited; (b) physically separate aerosol generating means (30; 54, 56) comprising at least one aerosol forming material and disposed between the ignited end (11) of the fuel element (10) and said rear end; marked by: (c) an elastic insulating member (86) which encloses at least a portion of the fuel element (10), has inorganic fibers and is at least 0.5 mm thick; and (d) an enclosure (46) for the insulating member (86). 2. Smoking article according to claim 1, which is designed as a cigarette-like article, wherein the fuel element (10), the aerosol generating means (30; 54, 56) and the insulating member (86) are designed and arranged for heat transfer from the fuel element (10) to the aerosol-forming material both during drawing and during smoldering. 3. Smoking article according to claim 1 or 2, wherein the fuel element (10) is arranged at the front end (11) of the article. 4. Smoking article according to one of the preceding claims, in which the fuel element (10) has at least one longitudinally extending passage (16). 5. Smoking article according to claim 4, wherein the fuel element (10) has a plurality of such passages (16). 6. Smoking article according to claim 4 or 5, in which at least one passage (16) has the shape of a hole. 7. Smoking article according to one of the preceding claims, in which the fuel element (10) has a length of approximately 30 mm or less prior to smoking. 8. A smoking article according to claim 7, wherein the fuel element (10) has a length of approximately 20 mm or less prior to smoking. 9. A smoking article according to claim 8, wherein the fuel element (10) has a length of approximately 15 mm or less prior to smoking. 10. Smoking article according to one of claims 7 to 9, wherein the fuel element (10) has a length prior to smoking of at least about 5 mm. 11. Smoking article according to one of the preceding claims, in which the fuel element (10) has a diameter between approximately 3 mm and 8 mm. 12. A smoking article according to claim 11, wherein the fuel element (10) has a diameter of about 4 mm to about 5 mm. 13. Smoking article according to one of the preceding claims, whose fuel element (10) has a density of at least 0.5 g/cm³. 14. A smoking article according to claim 13, wherein the fuel element (10) has a density in the range of about 0.5 g/cm³ to about 1.5 g/cm³. 15. Smoking article according to claim 13 or 14, the fuel element (10) of which has a density of more than about 0.7 g/cm³. 16. A smoking article according to any one of claims 13 to 15, wherein the fuel element has a density of at least about 0.8 g/cm³. 17. Smoking article according to one of the preceding claims, the fuel element (10) of which is a carbon fuel element. 18. Smoking article according to claim 17, the fuel element (10) of which contains at least about 50% by weight of carbon as such. 19. Smoking article according to claim 18, whose fuel element (10) contains at least 60 wt.% to 80 wt.% carbon . 20. A smoking article according to claim 19, wherein the fuel element (10) contains at least about 80% carbon by weight. 21. A smoking article according to claim 20, wherein the fuel element (10) contains at least about 85% carbon by weight. 22. Smoking article according to one of the preceding claims, the fuel element (10) has a tapered end to be ignited. 23. Smoking article according to one of the preceding claims, the fuel element (10) of which is a pressed or extruded carbon mass. 24. Smoking article according to one of the preceding claims, the fuel element (10) of which is substantially free of volatile organic material. 25. Smoking article according to one of the preceding claims, in which the components of the mass forming the fuel element (10) are selected so that no significant visible sidestream smoke is produced during smoldering. 26. A smoking article according to any preceding claim, further comprising an insulating member (86) designed and arranged to increase heat transfer from the fuel element (10) to the aerosol generating means (30; 54, 56). 27. Smoking article according to one of the preceding claims, in which the insulating member (86) encloses at least a portion of the aerosol generating means (30; 54, 56). 28. Smoking article according to one of the preceding claims, in which the aerosol generating means (30; 54, 56) are arranged in a container (87; 52). 29. Smoking article according to one of the preceding claims, in which a heat transfer member (87; 52) is provided to transfer heat generated by the fuel element (10) to the aerosol generating means (30; 54, 56) substantially during the entire burning time of the fuel element. 30. Smoking article according to one of the preceding claims, in which a heat transfer member (87; 52) is provided which contacts or overlaps at least a portion of the fuel element (10) and the aerosol generating means (30; 54, 56). 31. Smoking article according to claim 29 or 30, wherein the heat transfer member (87; 52) comprises at least a portion of the aerosol generating means (30; 54, 56). 32. A smoking article according to any one of claims 29 to 31, wherein the heat transfer member is located at least partially within the fuel element. 33. Smoking article according to one of claims 29 to 32, in which the heat transfer member (87; 52) encloses a portion of the longitudinally extending outer periphery of the fuel element (10) and the aerosol generating means (30; 54, 56). 34. Smoking article according to one of claims 29 to 33, in which the heat transfer member is a heat-conducting container (52) for the aerosol generating means (54, 56). 35. Smoking article according to claim 34, wherein an end of the heat-conducting container (52) facing the fuel element contacts a rear part of the fuel element (10). 36. Smoking article according to one of claims 29 to 35, in which the heat transfer member (87; 52) is located at a distance behind the end (11) of the fuel element (10) to be ignited. 37. Smoking article according to one of claims 29 to 36, in which the heat transfer member (87; 52) is a metallic member, preferably made of aluminum. 38. Smoking article according to one of claims 28 to 37, in which the container (87; 52) is a heat-conducting metallic tube. 39. A smoking article according to any one of claims 28 to 38, wherein the container (87) overlaps the rear portion of the fuel element (10), surrounds the aerosol generating means (30) and allows the passage of air and the aerosol forming material. 40. A smoking article according to any one of claims 29 to 39, wherein the heat transfer member comprises a conductive rod embedded in at least a portion of the fuel element and in a portion of the aerosol generating means. 41. A smoking article according to any one of claims 34 to 40, which comprises an insulating member (86) comprising at least a portion of the conductive container (87; 52). 42. Smoking article according to one of the preceding claims, wherein the insulating member (86) is non-combustible. 43. A smoking article according to any preceding claim, wherein the insulating member (86) is approximately 1 mm to 2.5 mm thick. 44. A smoking article according to claim 43, wherein the insulating member (86) is approximately 1 mm to 2 mm thick. 45. Smoking article according to one of the preceding claims, in which the insulating member (86) comprises an air-permeable mass of inorganic fibers. 46. Smoking article according to one of the preceding claims, in which the insulating member (86) is an air-permeable, elastic sleeve made of fibers. 47. A smoking article according to any preceding claim, wherein the insulating member (86) has a thermal conductivity of less than about 0.005 g-cal/(sec) (cm²) (°C/cm). 48. A smoking article according to any preceding claim, wherein the insulating member (86) contains a material which melts during use. 49. A smoking article according to claim 48, wherein the insulating member (86) comprises inorganic fibers which melt during use. 50. A smoking article according to any preceding claim, wherein the insulating member (86) comprises a low temperature grade of glass fibers. 51. A smoking article according to claim 50, wherein the insulating member (86) comprises glass fibers having a softening point below about 650°C. 52. Smoking article according to one of the preceding claims, in which a tobacco charge (56) is provided. 53. Smoking article according to claim 52, wherein the tobacco charge (56) is arranged between the rear end of the fuel element (10) and the mouth end (15) of the smoking article. 54. Smoking article according to one of the preceding claims, in which tobacco is arranged between the aerosol generating means and the mouth end of the smoking article. 55. A smoking article according to claim 54, wherein the tobacco is located at the rear end of the aerosol generating means. 56. A smoking article according to any preceding claim, which has a quantity of tobacco extract between the rear end of the fuel element and the mouth end of the smoking article. 57. Smoking article according to one of the preceding claims, in which - in the longitudinal direction of the smoking article - the aerosol generating means (30; 54, 56) are arranged adjacent to the fuel element (10). 58. Smoking article according to one of the preceding claims, in which the aerosol generating means (30; 54, 56) are arranged very close to the fuel element (10). 59. Smoking article according to one of the preceding claims, in which the aerosol generating means (30; 54, 56) are adjacent to the fuel element (10). 60. Smoking article according to one of the preceding claims, in which the fuel element (10) and the aerosol generating means (30; 54, 56) are in heat exchange with one another based on thermal conduction such that heat is supplied to the aerosol generating means (30; 54, 56) by thermal conduction substantially during the entire burning time of the fuel element (10). 61. Smoking article according to claim 60, in which the fuel element (10) and the aerosol generating means (30; 54, 56) are in conductive heat exchange with one another by contact between the aerosol generating means and a portion of the fuel element. 62. Smoking article according to one of the preceding claims, in which the aerosol generating means (30; 54, 56) are arranged so that their distance from the end (11) of the fuel element (10) to be ignited is not more than approximately 30 mm. 63. Smoking article according to claim 62, in which the aerosol generating means (30; 54, 56) are arranged so that their distance from the end (11) of the fuel element (10) to be ignited is not more than approximately 15 mm. 64. Smoking article according to one of the preceding claims, in which the aerosol generating means (30; 54, 56) are loaded with approximately 20 mg to 120 mg of aerosol-forming material. 65. Smoking article according to claim 64, wherein the aerosol generating means (30; 54, 56) are loaded with 35 mg to 85 mg aerosol forming material. 66. A smoking article according to any preceding claim, wherein under smoking conditions with puffs of 35 ml and 2 seconds in duration separated by smolders of 58 seconds in duration, more than about 15% by weight of the aerosol-forming material carried by the aerosol generating means (30; 54, 56) is delivered as a total amount of wet particles. 67. A smoking article according to any preceding claim, which, under smoking conditions with 35 ml puffs of 2 seconds duration separated by smoldering periods of 58 seconds duration, delivers at least about 0.6 mg total moist particles in the first three puffs. 68. A smoking article according to any preceding claim, the aerosol generating means (30; 54, 56) of which are loaded with sufficient aerosol forming material to cause the smoking article to deliver, under smoking conditions with puffs of 35 ml and 2 seconds duration separated by glosts of 58 seconds duration, at least about 1.5 mg total of moist particles during the first three puffs. 69. A smoking article according to any preceding claim, wherein the aerosol generating means (30; 54, 56) are loaded with sufficient aerosol forming material to cause the smoking article to be released under smoking conditions with puffs of 35 ml and 2 seconds duration, which are Glosten separated by 58 seconds, with at least six puffs releasing on average at least approximately 0.8 mg total amount of moist particles per puff. 70. A smoking article according to claim 69, which delivers, under smoking conditions with 35 ml puffs of 2 seconds duration separated by smoldering periods of 58 seconds, over at least ten puffs, an average of at least 0.8 mg of total moist particles per puff. 71. Smoking article according to one of claims 28 to 70, in which the container (52) is bent at its mouth-side end. 72. Smoking article according to one of the preceding claims, whose aerosol generating means (30; 54, 56) contain a tobacco extract. 73. Smoking article according to one of the preceding claims, in which volatile or vaporizable odor or flavor agents are arranged between the aerosol generating means (30; 54, 56) and the mouth-side end (15). 74. Smoking article according to one of the preceding claims, in which the smoke produced consists essentially of oxides of carbon, air, water, volatile substances contained in the aerosol generating means (30; 54, 56), other desired volatile substances and traces of other materials. 75. A smoking article according to any one of claims 17 to 74, which, as measured by the Ames test, shows no mutagenic activities in the total amount of wet particles. 76. A smoking article according to any preceding claim, which has a diameter of about 8 mm or less. 77. A smoking article according to any preceding claim, which has the size and shape of a cigarette. 78. Smoking article according to one of the preceding claims, which additionally comprises a mouth end piece (40). 79. A smoking article according to claim 78, which comprises means (44) for delivering the aerosol forming material to the user, wherein said mouth end piece (40) and the aerosol delivery means (44) extend for more than half the length of the smoking article. 80. A smoking article according to any preceding claim, which delivers a visible smoke-like aerosol. 81. A smoking article according to any preceding claim, which is adapted for use with a separate mouthpiece. 82. Smoking article according to one of the preceding claims, which further comprises means (52, 44; 87, 44) for directing the gases of the fuel element (10) through the aerosol generating means (30; 54, 56) and to the mouthpiece (45). 83. Smoking article according to one of the preceding claims, the aerosol generating means (30; 54, 56) of which comprise a thermally stable substrate (30; 54) which carries the aerosol-forming material. 84. Smoking article according to claim 83, the thermally stable substrate (54) of which contains ceramic material. 85. Smoking article according to one of the preceding claims, the aerosol generating means (54, 56) of which comprise a particulate substrate (54). 86. A smoking article according to any preceding claim, further comprising a filter (45). 87. Smoking article according to one of the preceding claims, in which the fuel element (10) and the aerosol generating means (30; 54, 56) are designed and arranged so that heat is transferred from the fuel element (10) to the aerosol generating means (30; 54, 56) in order to volatilize the aerosol-forming material during the draw throughout the smoking process. 88. Smoking article according to one of claims 1 to 60 and 62 to 87, in which the aerosol generating means (30) contact the fuel element (10) in order to receive heat from the fuel element substantially throughout the entire burning time of the fuel element. 89. Smoking article according to one of the preceding claims, wherein during use the burning of the fuel element (10) does not produce any removable ash.