DE3587952T2 - 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 cigarette-like smoking article which produces an aerosol which is similar to tobacco smoke and contains no more than a minimal amount of incompletely burned combustion or pyrolysis products, as defined in the preamble of claims 1 and 2.

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.

EP-A-0 117 355 (Hearn et al.) describes a proposed cigarette-like smoking article having a carbon heat source with an axial passage and a separate aroma generator (taste and odor generator). The formation of the heat source (page 2, line 23 to page 7, line 14) is carried out by pyrolyzing a preformed, tubular lignocellulosic pulp material of e.g. 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 8-27) has a substrate, such as tobacco, alumina, etc., located near the mouth end, which is impregnated with or inherently contains at least one heat-releasable flavoring agent. The aroma generator can also have a flavored, foamed core inside of the heat source. A conventional filter can 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 lignocellulosic material undergoes a maximum dimensional shrinkage of 37.5% (see page 12, lines 3 and 4), so that from a tubular lignocellulosic material with a length of 65 mm, a carbon heat source with a length of over 40 mm is obtained.

US-A-4 340 072 also describes a proposed cigarette-like smoking article which has a rod-like fuel element with a central axial passage, aerosol generating means defined by a chamber and a short filter tip arranged one behind the other. The total length of the smoking article is 70 mm and its diameter is 7 mm. The fuel element is a part moulded or extruded from reconstituted tobacco and/or tobacco substitute, e.g. a mixture of carbon and a binder (NaCMC), and the front end of its axial passage can be closed with a plug made of the same material to prevent the penetration of a pilot flame into the central axial passage of the fuel element. 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 accompanying 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, i.e. about 51 mm.

Likewise, EP-A-0 074 201 describes a proposed cigarette-like smoking article with a combustible carbonized rod which may contain either a filter with a length of 10 mm up to 40 mm or is the sole fuel element of a tobacco-free cigarette, the fuel element having a length of 85 mm to 120 mm. If the combustible carbonized rod is used as a filter in this known smoking article, then the known smoking article has a tobacco column which extends over approximately half the total length of the smoking article and is arranged in front of the filter. When such an embodiment of the known smoking article is smoked, the carbon filter supposedly retains the particulate phase (TPM), and when the smoldering zone reaches the carbon filter, it burns in a similar way to the tobacco column, but it does not release its own TPM and only releases small amounts of the retained and condensed TPM resulting from the combustion of the tobacco column.

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 and pyrolysis products.

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

Starting from a cigarette-like smoking article with a mouth end which comprises a fuel element which mainly comprises carbon as such and has an ignited end and a rear end, as well as with physically separate aerosol generating means which comprise an aerosol-forming material and are arranged between the ignited end of the fuel element and the mouth end, this object is achieved according to the invention by a design of a smoking article such that the fuel element is less than approximately 30 mm long before smoking and is designed and arranged such that it burns during the entire smoking process in order to generate heat for volatilization aerosol-forming material when pulling during the entire smoking process.

Starting from a cigarette-like smoking article with a mouth end which comprises a fuel element with a density of at least 0.5 g/cm³, an end to be lit and a rear end, and with physically separate aerosol generating means which comprise an aerosol-forming material and are arranged between the end of the fuel element to be lit and the mouth end, this object is achieved according to the invention by a design of a smoking article such that the fuel element is less than approximately 30 mm long before smoking and is designed and arranged such that it burns during the entire smoking process in order to generate heat for volatilizing aerosol-forming material when drawing during the entire smoking process.

In all of the above smoking articles according to the invention, the heat generated by the fuel element during smoking is used more effectively to form an aerosol that resembles the smoke of a conventional cigarette-like smoking article.

Further advantageous features of the cigarette-like smoking article according to the invention are described in the appended claims 3 to 95.

The present invention provides a cigarette-like smoking article capable of generating substantial amounts of aerosol both initially and during the useful life of the product, without significant thermal decomposition of the aerosol-forming material, without the occurrence of substantial amounts of pyrolysis or incompletely burned combustion products, and preferably without substantial amounts of sidestream smoke.

Preferably, the heat exchange between the fuel element and the aerosol generating means is carried out by means of a heat transfer element, preferably a heat-conducting element, such as 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 preferably provided with a peripheral insulating element, such as a sleeve made of insulating fibers, this sleeve preferably 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 minimizing the effect of the substrate as a heat sink. Since the aerosol forming substance and the fuel element are physically separated from each other, the aerosol forming substance is exposed to temperatures significantly 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 substances 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, in order to be used in conjunction with a separate mouthpiece for single or multiple use.

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, but 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 2 second puffs (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 provide of the invention under FTC smoking conditions averages a total amount of wet particles of at least about 0.8 mg per puff 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 substantially 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 that are perceived by the user as "smoke-like" and that 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 agents, regardless of whether they generate 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 during substantially the entire burning time of the fuel element. Conductive heat exchange can be achieved by arranging the aerosol generating means so that it is in direct contact with the fuel element and 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 heat transfer by conduction.

In the present description, the term "carbon(-)" means "containing predominantly carbon as such".

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).

An advantageous embodiment of the invention comprises a combustible fuel element with a length of less than 30 mm and a density of at least 0.5 g/cm³, aerosol generating means in heat exchange with the fuel element based on thermal conduction, and means for delivering the aerosol formed by the aerosol generating means to the user.

A preferred embodiment comprises a fuel element, physically separate aerosol generating means comprising an aerosol-forming material, and an insulating element which encloses at least a portion of the fuel element. Preferably, the fuel element and the aerosol generating means in a heat exchange based on heat conduction. For this embodiment, it is also proposed to use a fuel element with a length of less than 30 mm.

Preferred embodiments of the invention are designed so that the smoking article has no mutagenic activity in the total amount of moist particles produced, measured according to the Ames test method.

In the embodiment comprising an insulating element, this insulating element is preferably elastic and has a minimum thickness of 0.5 mm.

Preferably, the insulating element comprises a fibrous material. Advantageously, the insulating element further encloses at least part of the aerosol generating means.

In an advantageous embodiment, the fuel element is a carbon material and less than 20 mm long.

Preferably, the fuel element is less than 15 mm long.

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 a 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 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.

Preferred embodiments of the smoking article according to the invention are designed to deliver a total amount of moist particles of at least about 0.6 mg in the first three puffs under FTC smoking conditions. Preferably, the smoking article delivers a total amount of moist particles of at least about 1.5 mg in the first three puffs under FTC smoking conditions. It is proposed that the smoking article be designed to deliver a total amount of moist particles of on average at least about 0.8 mg per puff over at least six puffs under FTC smoking conditions.

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.

The fuel element preferably comprises carbon-containing material. Preferably, in this case too, the fuel element is less than 20 mm and even more advantageously less than 15 mm long.

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 comprise 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. It is proposed to use an insulating element which is elastic and at least 0.5 mm thick.

Preferred embodiments of the smoking article according to the invention are explained in more detail in the accompanying drawings and the following detailed description of the invention.

BRIEF DESCRIPTION OF THE CHARACTERS

Figures 1 to 9 show various embodiments of the invention in longitudinal section. They also show:

Figure 1A is a section through the embodiment of Figure 1 along the line 1A-1A in Figure 1;

Figure 2A is a longitudinal section of a modified tapered fuel element of the embodiment of Figure 2;

Figure 3A is a section through the embodiment of Figure 3 along the line 3A-3A of Figure 3; and

Figure 10 shows the average peak temperature profile of the smoking article of Example 5 during use.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment of the invention shown in Figure 1, which preferably has the diameter of a conventional cigarette, comprises a short, combustible carbon fuel element 10, an aerosol generating means 12 abutting thereon and a foil-lined paper tube 14 which forms the mouthpiece 15 of the smoking article. In this embodiment, the fuel element 10 is a "blowpipe charcoal", i.e., charred wood provided with five longitudinally extending holes 16. See Figure 1A. The approximately 20 mm long fuel element 10 may optionally be wrapped in cigarette paper to improve the lighting of the charcoal fuel. This paper may be treated with known burn-modifying additives.

The aerosol generating means 12 comprises a plurality of glass beads 20 coated with one or more aerosol forming substances such as glycerol. The glass beads are held in place by a porous disk 22 which may be made of cellulose acetate. This disk may be provided with a series of circumferential grooves 24 to create passages between the disk and the foil-lined tube 14.

The foil-lined paper tube 14, which forms the mouthpiece of the smoking article, encloses the aerosol generating means 12 and the rear, non-ignitable end of the fuel element 10. The tube also forms an aerosol delivery passage 26 between the aerosol generating means 12 and the mouthpiece 15 of the smoking article.

The foil-lined tube 14, which connects the non-ignitable end of the fuel 10 to the aerosol generator 12, also provides increased heat transfer to the aerosol generator. The foil also helps to extinguish the ember cone. Once only a small amount of unburned fuel remains, the heat loss through the foil acts as a heat sink and thus assists in extinguishing the ember cone.

The foil used in this smoking article is typically 0.35 mil (0.0089 mm) thick aluminum foil, but the thickness and/or type of metal used can be varied to achieve any desired level of heat transfer. Other types of heat-conducting elements can also be used, such as the "Grafoil" product available from Union Carbide.

Optionally, the smoking article shown in Figure 1 also includes a tobacco charge or plug 28 to add flavor to the aerosol. This tobacco charge 28 may be located at the mouth end of the disk 22, as in Figure 1, or between the glass beads 20 and the disk 22. It may also be located in the passage 26, spaced from the aerosol generator 12.

In the embodiment shown in Figure 2, the short fuel element 10 is a pressed carbon rod or plug with a length of approximately 20 mm and an axial hole 16. Alternatively, the fuel can be formed from carbonized fibers and preferably also with an axial hole corresponding to the hole 16. passage. In this embodiment, the aerosol generating means 12 comprises a heat-resistant, conductive carbon substrate 30, such as a plug of porous carbon impregnated with one or more aerosol-forming substances. This substrate can optionally be provided with an axial passage 32 as shown in Figure 2. Furthermore, this embodiment comprises a quantity of tobacco 28, preferably arranged at the mouth end of the substrate 30. For optical reasons, this smoking article optionally also has a highly porous cellulose acetate filter 34, which can be provided with peripheral grooves 36 in order to create passages for the aerosol-forming substance between the filter 34 and the foil-lined tube 14. Optionally, the ignitable end 11 of the fuel element can be tapered, as shown in Figure 2A, in order to improve ignitability.

The embodiment of the invention shown in Figure 3 comprises a short combustible carbon fuel element 10 connected to aerosol generating means 12 via a heat conductive rod 99 and a foil lined paper tube 14, which paper tube also leads to the mouth end 15 of the smoking article. In this embodiment, the fuel element 10 may be a blowpipe carbon or a pressed or extruded carbon rod or plug or other carbon fuel source.

The aerosol generating means 12 comprises a heat-resistant carbon substrate 30, for example a plug of porous carbon impregnated with one or more aerosol forming substances. This embodiment has a void 97 between the fuel element 10 and the substrate 30. The portion of the foil-lined tube 14 enclosing this void has a plurality of circumferential holes 100 which allow sufficient air to enter the void to provide adequate pressure drop.

As shown in Figures 3 and 3A, the heat conducting means comprise a conductive rod 99 and the foil lined tube 14. The rod 99, preferably made of aluminum, has at least one, preferably 2 to 5, circumferential grooves 96 which allow air to pass through the substrate. The smoking article according to Figure 3 offers the advantage that the air introduced into the empty space 97 contains fewer carbon oxidation products because it is not drawn in by the burning fuel.

The embodiment shown in Figure 4 comprises a fibrous carbon fuel element 10, such as carbonized cotton or rayon. The fuel element comprises a single axial hole 16. The substrate 38 of the aerosol generator is a granular, heat-resistant carbon. Immediately behind the substrate is a quantity of tobacco 28. This smoking article comprises a cellulose acetate tube 40 instead of the foil-lined tube of previous embodiments. This tube 40 comprises an annular region 42 of cellulose acetate strand material which encloses an optional plastic tube 44, e.g. of polypropylene. At the mouth end 15 of this element is a low efficiency cellulose acetate filter plug 45. The smoking article is wrapped with cigarette paper 46 along its entire length. At the mouth end, a covering 48 with cork or white print can be used as a mouthpiece imitation. On the inside of the paper, towards the fuel-side end of the smoking article, there is a foil strip 50. This strip preferably extends from the rear part of the fuel element to the mouth end of the tobacco charge 28. It can form a unit with the paper or be designed as a separate part applied in front of the paper wrapping.

The embodiment of Figure 5 is similar to that shown in Figure 4. In this embodiment, the aerosol generating means 12 are formed by an aluminum macrocapsule 52 which is coated with a granular substrate or, as in the drawing, shown, a mixture of granular substrate 54 and tobacco 56. The macrocapsule 52 is bent at its ends 58, 60 to confine the material and inhibit migration of the aerosol generator. The fuel-side bent end 58 preferably abuts against the rear end of the fuel element to allow heat transfer by conduction. A void 62 formed by the end 58 also helps to inhibit migration of the aerosol generator toward the fuel. Longitudinal passages 59 and 61 are provided to allow passage of air and the aerosol-forming substance. The macrocapsule 52 and the fuel element 10 can be joined together by means of a conventional cigarette paper 47 as shown in the drawing, a perforated ceramic paper or a foil strip. When using cigarette paper, a strip 64 near the rear end of the fuel should be printed or treated with sodium silicate or other known substances which cause the paper to extinguish. The smoking article is wrapped over its entire length with conventional cigarette paper 46.

Figure 6 shows another embodiment using a pressed carbon fuel plug 10. In this embodiment, the fuel element has a tapered ignition end 11 to facilitate ignition and a tapered rear end 9 to facilitate insertion into a tubular foil envelope 66. Adjacent to the rear end of the fuel element is an aluminum disk 68 having a central hole 70. A second, optional aluminum disk 72 having a hole 74 is located at the mouth end of the aerosol generator 12. Between them is a particulate substrate zone 76 and a tobacco zone 78. The foil envelope 66 in which the fuel element is located extends rearwardly beyond the second aluminum disk 72. This embodiment also includes a hollow cellulose acetate rod 42 with an internal polypropylene tube 44 and a cellulose acetate filter plug 45. The smoking article is preferably wrapped over its entire length with cigarette paper 46.

The embodiment shown in Figure 7 shows the use of a substrate 80 embedded in a large cavity 82 in the fuel element 10. In this embodiment, the fuel element is preferably formed from an extruded carbon and the substrate 80 is typically a relatively rigid, porous material. The entire length of the smoking article is wrapped in conventional cigarette paper 46. This embodiment may also include a foil strip 84 to connect the fuel element 10 to the cellulose acetate tube 40 and to assist in extinguishing the fuel.

The embodiments shown in Figures 8 and 9 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 8, 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 instead of the ceramic fibers. The fuel element 10 is preferably an extruded carbon plug with a hole 16. In the embodiment shown, the end 11 to be lit projects slightly beyond the edge of the sleeve 86 to facilitate lighting. 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 with a mouth end piece, such as the elongated one shown in the drawing. Cellulose acetate tube 40. The sleeve 86 extends to the mouth end of the substrate 30, but can also replace the cellulose acetate rod 42.

In the embodiment of Figure 9, an aluminum macrocapsule 52 of the type shown in Figure 5 is used, which surrounds a granular substrate 54 and tobacco 56. This macrocapsule is preferably arranged completely within the insulating sleeve 86. In addition, the end 11 of the fuel element 10 to be lit 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 in a form similar to that shown in Figure 8.

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 brought to the diameter of a conventional cigarette with a glass fiber wrap.

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 limit, orient and concentrate the 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 elements 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 combine with the aerosol generator to produce a system that is capable of producing significant amounts of aerosol with practically every puff. The fact that the aerosol generator is in close proximity to the glowing cone after a few puffs, in conjunction with the insulating means, 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, e.g., 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, the insulating sleeve, the paper wrapping and the 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 long. 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 description was in a range of 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 the holes 16 in Figures 1 to 5. These holes impart porosity and increase the 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 any binders, combustion-modifying additives, moisture, etc.

The carbon materials used with or as the preferred fuel can be obtained from virtually any of the numerous carbon sources known in the art. Preferably, the carbon material is obtained 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. Combustion properties of this type can generally be achieved with cellulosic material which has been pyrolyzed at temperatures between about 400ºC to about 1000ºC, preferably between about 500ºC to about 950ºC, 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 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 650 ºC, 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 the mixture of substances may be in a range up to approximately 500 ºC. Substances which have these properties include, for example, polyhydric alcohols such as glycerol and propylene glycol, as well as 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 transfer. As shown in the illustrated embodiments, the heat-conducting element is preferably arranged to contact a portion of the fuel element and the aerosol generating means. or overlaps, 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 designations 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 ºC.

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 also 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 include the foil lined tube used in the embodiments of Figures 1 to 3 and the cellulose acetate tube used in the embodiments of Figures 4 to 9. 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. Furthermore, the smoking article may 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 from air, carbon oxides, the aerosol carrying the desired flavorings or other desired volatiles, water, and traces of other substances. The total moist 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 further explained with reference to the following examples, which serve to better understand the present invention, but are not intended to limit the present invention thereto. The percentages given herein are percentages by weight, unless otherwise stated. All temperatures are expressed in degrees Celsius and are unadjusted. In all cases, the smoking articles have a diameter of approximately 7 to 8 mm, the diameter of a conventional cigarette.

example 1

A smoking article was prepared in accordance with the embodiment of Figure 1. The fuel element was a 25 mm long piece of blowpipe charcoal with five longitudinal passages 0.040 inches (1.02 mm) in diameter made with a No. 60 drill. The charcoal weighed 0.375 g. The fuel element was wrapped in conventional treated cigarette paper. The substrate was 500 mg of glass beads (average diameter 0.64 inches (1.63 mm)) coated with a layer of two drops (about 50 mg) of glycerol. When placed in the tube, this substrate was about 6.5 mm long. The foil-lined tube consisted of a 0.35 mil (0.0089 mm) layer of aluminum foil inside a 4.25 mil (0.108 mm) layer of white spiral-wound paper. This tube encased the rear 5 mm of the fuel element. A short piece of cellulose acetate (8 mm) with four grooves around the circumference was used to hold the glass beads against the fuel source. An additional grooved cellulose acetate filter piece 8 mm long was inserted into the mouth end of the tube to give the smoking article the appearance of a conventional cigarette. The total length of the smoking article was approximately 70 mm.

Designs of this type produced significant aerosol quantities on the lighting puff, reduced aerosol quantities on the 2nd and 3rd puffs, and good aerosol delivery values on puffs 4 to 9. Designs of this type typically produced a total wet particle quantity (WTPM) of approximately 5-7 mg when smoked mechanically under FTC smoking conditions with a puff volume of 35 ml, a puff duration of two seconds, and a puff frequency of 60 seconds.

Example 2

A. Four smoking articles were prepared using 10 mm long pressed carbon fuel elements and glass bead substrates. The fuel elements were made of 90% PCB-G and 10% NaCMC with approximately 5000 pounds (2273 kg) of stress and formed with a tapered lighting end as shown in Figure 2A. Each element was provided with a single 0.040 inch (1.02 mm) diameter opening along its center. Three of the four fuel sources were wrapped with 8 mm wide strips of conventional cigarette paper. The fuel elements were inserted into 70 mm long sections of the foil lined tube described in Example 1 for a length of approximately 2 mm. Glass beads coated with glycerol in the amounts shown in the table below were placed in the open end of the foil-lined tube and held against the fuel element by 5 mm long foamed polypropylene filters having a series of longitudinally extending circumferential grooves. A 5 mm long low efficiency cellulose acetate filter pad was inserted into the mouth end of each smoking article. These smoking articles were machine smoked under FTC smoking conditions and the total wet particulate matter (WTPM) was collected on a series of so-called Cambridge filters. The results of these experiments are shown in Table I. TABLE I Glass beads (weight) Aerosol generator (weight) WTPM (mg)/puffs *The fuel stick in this version was not wrapped in cigarette paper

B. Three smoking articles similar to that described in Example 2A were prepared using 20 mm long blowpipe carbon fuel elements of the type described in Example 1. These smoking articles were machine smoked under FTC smoking conditions and the total wet particulate matter (WTPM) was collected on a series of Cambridge filters. The results of these tests are presented in Table II. TABLE II Glass beads (weight) Aerosol generator (weight) WTPM (mg)/puffs *The fuel stick in this version was not wrapped in cigarette paper

Example 3

A. Four smoking articles were prepared as shown in Figure 2, having a 10 mm long, pressed carbon fuel element with a tapered igniting end as shown in Figure 2A. The fuel element was made from 90% PCB-G and 10% NaCMC with approximately 5000 pounds (2273 kg) of loading. The element was drilled with a 0.040 inch (1.02 mm) hole down its center. The substrate for the aerosol generator was cut and mechanically formed from PC-25, a carbon sold by Union Carbide Corporation, Danbury, CT. The substrate for each smoking article was approximately 2.5 mm long and approximately 8 mm in diameter. It was loaded with an average of approximately 27 mg of a 1:1 propylene glycol/glycerol mixture. The mouthpiece, formed as a foil-lined tube, of the same type as used for Example 1, enclosed the rear 2 mm of the fuel element and the substrate. A plug of Burley tobacco in an amount of approximately 100 mg was placed against the mouth end of the substrate. A short polypropylene filter piece, approximately 5-9 mm long, with baffles was placed in the mouthpiece of the foil-lined tube. A 32 mm long cellulose acetate filter with a hollow polypropylene tube in the core was placed between the tobacco and the filter piece. Each smoking article had a total length of approximately 78 mm.

B. Six additional smoking articles were prepared substantially in accordance with Example 3A, except that the length of the substrate was increased to 5 mm and a 0.040 inch (1.02 mm) hole was provided through the substrate. Furthermore, these smoking articles were made without cellulose acetate/polypropylene tubes. Approximately 42 mg of the propylene glycol/glycerol mixture was applied to the substrate. Two plugs of Burley tobacco were also used in an amount of 100-150 mg each.

The first was placed against the mouth end of the substrate and the second against the filter piece.

C. Four additional smoking articles were prepared substantially in accordance with Example 3A, except that instead of the plug of burley tobacco, a plug of hot air cured tobacco containing about 6% by weight diammonium monohydrogen phosphate was used.

The smoking articles of Examples 3A-C were subjected to the standard Ames test. See Ames et al., Mut. Res., 31:347-364 (1975), as modified by Nagas et al., Mut. Res., 42:335 (1977) and 113:173-215 (1983). Samples 3A and 3C were smoked using a conventional cigarette smoking machine under smoking conditions with puffs of 35 ml volume, 2 seconds duration and a frequency of 30 seconds for 10 puffs. The smoking articles of Example 3B were smoked in the same manner except that a puff frequency of 60 seconds was used. Only one filter pad was used for each group of smoking articles. This resulted in the following total moist particulate matter (WTPM) for the groups of smoking articles indicated:

WTPMS

Example 3A 63.4 mg

Example 3B 50.6 mg

Example 3C 69.2 mg

The filter pads containing the separated WTPM used for each of the above examples were shaken in DM50 for 30 minutes to dissolve the WTPM. Each sample was then diluted to a concentration of 1 mg/ml and used as such for the Ames test. Using the method of Nagas et al., Mut. Res., 42:335-342 (1977), WTPM sample concentrations of 1 mg/ml were mixed into the S9 activation system and standard Ames bacterial cells and at 37ºC for twenty minutes. For this Ames test, bacteria of the Salmonella typhimurium strain TA 98 were used. See Purchase et al., Nature, 264:624-627 (1976). Agar was then added to the mixture and plate cultures were prepared. The agar plates were incubated for two days at 37ºC and the resulting cultures were counted. Four plates were examined per dilution and the standard deviation of the colonies was compared with a pure DMSO control culture. As can be seen in Table III, no mutagenic activity caused by the WTPM could be detected in any of the smoking articles tested. This can be determined by comparing the average number of revertants per plate with the average number of revertants from the control sample (0 ug WTPM/plate). In mutagenic samples, the average number of revertants per plate also increases with increasing dose. TABLE III Example 3A Dose (ug WTPM/plate) Average No. of revertants/plate Standard deviation control Example 3B Dose (ug WTPM/plate) Average number of revertants/plate Standard deviation Control Example 3C Dose (ug WTPM/plate) Average number of revertants/plate Standard deviation Control

Example 4

Five smoking articles were made as shown in Figure 2. Each smoking article had a 10 mm long compressed carbon fuel source as described in Example 3A. This fuel element was inserted for a length of 3 mm into one end of a 70 mm long aluminum foil lined tube as described in Example 1. A 5 mm long carbon felt substrate cut from rayon carbon felt sold by Fiber Materials Inc. was placed against the fuel source. This substrate was coated with an average of approximately 97 mg of a 1:1 mixture of glycerol and propylene glycol, approximately 3 mg of nicotine and approximately 0.1 mg of a flavor mixture. A 5 mm long section of a tobacco mixture ("blend") was placed against the mouth end of the substrate. A 5 mm long piece of cellulose acetate filter was placed in the mouth end of the foil-lined tube.

These smoking articles were mechanically smoked under FTC smoking conditions. The aerosol from these smoking articles (133.3 mg WTPM) was collected on a single Cambridge filter, diluted in DMSO to a final concentration of 1 mg WTPM per ml, and assayed for Ames activity as described in Example 3D using the following strains: Salmonella typhimurium TA 1535, 1537, 1538, 98, and 100. As shown in Table IV, no mutagenic activity caused by the WTPM isolated from the smoking articles was detected. TABLE VI Dose* Average number of revertants Control *ug WTPM/plate

Example 5

A smoking article according to Figure 2 was prepared with a 10 mm long pressed carbon fuel plug in the form shown in Figure 2A, but without tobacco. The fuel element was made from a mixture of 90% activated carbon PCB-G and 10% NaCMC as a binder with approximately 5000 pounds (2273 kg) loading. The fuel element was provided with a 0.040 inch (1.02 mm) longitudinal bore. The substrate was a 10 mm long porous carbon plug made of PC-25 material sold by Union Carbide. It was provided with an axial bore of 0.029 inch (0.74 mm) and loaded with 40 mg of a 1:1 mixture of propylene glycol and glycerol. The foil-lined tube of the type described in Example 1 encircled the rear 2 mm of the fuel element and formed the mouthpiece. The smoking article had no filter tip, but was wrapped in conventional cigarette paper. The total length of the smoking article was 80 mm.

The average peak temperatures of this smoking article during drawing and smoldering are shown in Figure 10. As shown, the temperature decreases steadily between the rear end of the fuel element and the mouth end. This ensures that the user does not experience an unpleasant burning sensation when using a product according to the invention.

Example 6

A smoking article was made according to the embodiment of Figure 3. The fuel element was a 19 mm long piece of soldering carbon without longitudinal passages. Embedded 15 mm deep in the fuel element was an aluminum rod with a diameter of 1/8 inch (3.2 mm) and a length of 28 mm. In the portion of the aluminum rod which penetrated the substrate, four circumferential grooves measuring 9 mm by 0.025 inch (0.64 mm) were made at 90° intervals. The substrate was Union Carbide PC-25 carbon 8 mm long. The grooves in the aluminum rod extended approximately 0.5 mm beyond the end of the substrate in the fuel side direction. The substrate was loaded with 150 mg of glycerol. The foil-lined tube, identical to that described in Example 1, encircled a portion of the rear portion of the fuel element. A gap was left between the non-burning end of the fuel element and the substrate. In the area of this gap, a series of holes were made through the foil-lined tube to allow air flow. A similar smoking article was made with a pressed carbon fuel plug.

Example 7

A smoking article as shown in Figure 4 was prepared with a fuel source formed from carbonized cotton fiber. Four cotton fiber ribbons were tightly braided together with cotton twine to form a strand approximately 0.4 inch (10.2 mm) in diameter. This material was placed in a nitrogen atmosphere furnace heated to 950 ºC. After the material reached this temperature in approximately 1 1/2 hours, it was held at that temperature for 1/2 hour. A 16 mm piece of this pyrolyzed material was cut for use as a fuel element. A 2 mm axial hole 16 was probed through the element. The fuel element was inserted for a length of 2 mm into a 20 mm long foil lined tube of the type described in Example 1. 100 mg of granulated PC-25 from Union Carbide containing 60 mg of a 1:1 mixture of propylene glycol/glycerol were placed in the foil-lined tube. Immediately behind the granulated Substrate A 5 mm long tobacco plug of approximately 60 mg was placed in the foil-lined tube. A 48 mm long ring-shaped cellulose acetate tube with an internal polypropylene tube having an inner diameter of 4.5 mm was inserted into the foil-lined tube for a length of approximately 3 mm. A second foil-lined tube of 50 mm length was placed over the cellulose acetate tube until it rested against the 20 mm foil-lined tube. A 5 mm long cellulose acetate filter plug was inserted into the end of this second foil-lined tube. The total length was 84 mm. The burning smoking article produced significant amounts of tobacco flavored aerosol throughout the first six puffs.

Example 8

A smoking article as shown in Figure 5 was prepared with a 15 mm long fibrous fuel element substantially as described in Example 7. The macrocapsule 52 was formed from a 15 mm long, 4 mil (0.10 mm) thick piece of aluminum foil bent to form a 12 mm long capsule. This macrocapsule was loosely filled with 100 mg of granulated PC-60, a carbon obtained from Union Carbide, and 50 mg of a tobacco blend. The granulated carbon was impregnated with 60 mg of a 1:1 mixture of propylene glycol and glycerol. The macrocapsule, fuel element and mouthpiece were assembled using an 85 mm long piece of conventional cigarette paper.

Example 9

A smoking article was manufactured according to the embodiment of Figure 6, which had a 7 mm long pressed carbon fuel element containing 90% carbon of the PXC type and 10% NaCMC. The longitudinal passage had a 0.040 inch (1.02 mm) diameter. This fuel plug was inserted into a 17 mm long aluminum foil lined tube so that 3 mm of the fuel element was inside the tube. An 8 mm diameter disk of 3.5 mil (0.089 mm) thick aluminum foil with a 0.049 inch (1.24 mm) diameter central hole was inserted into the other end of the tube so that it rested against the end of the fuel source.

A PG-60 grade carbon from Union Carbide was granulated and sieved to a particle size of -6 to +10 mesh. 80 mg of this material was used as a substrate, and this substrate was loaded with 80 mg of a 1:1 mixture of glycerol and propylene glycol. The impregnated granules were placed in the foil-lined tube so that they rested against the foil disk at the end of the fuel source. A 50 mg tobacco blend was placed so that it rested loosely against the substrate granules. An additional foil disk with a 0.049 inch (1.24 mm) central hole was placed in the foil-lined tube at the mouth end of the tobacco. A long, hollow cellulose acetate rod was inserted into the foil-lined tube, with a hollow polypropylene tube of the type described in Example 7, for a length of 3 mm. A second foil-lined tube was placed over the cellulose acetate rod, toward the end of the 17 mm foil-lined tube.

When smoked under FTC smoking conditions, this version delivered 11.0 mg of aerosol with the first three puffs. In total, the aerosol delivery from nine puffs was 24.9 mg.

Example 10

A smoking article was manufactured with a fuel element and substrate designed as shown in Figure 7, wherein a 15 mm long, ring-shaped, pressed carbon fuel element with an inner diameter of approximately 4 mm and an outer diameter of approximately 8 mm was used. The fuel was made from 90% PCB-G activated carbon and 10% NaCMC. The substrate was a 10 mm long piece of Union Carbide PC-25 carbon with an outer diameter of approximately 4 mm. The substrate, loaded with 55 mg of a 1:1 mixture of glycerol/propylene glycol, was inserted into the area of the fuel end closest to the mouth end of the smoking article. This fuel/substrate combination was inserted over a length of 7 mm into a 70 mm foil-lined tube which had a short cellulose acetate filter at the mouth end. The length of the smoking article was approximately 77 mm.

The smoking article delivered significant amounts of aerosol during the first three puffs and over the life of the fuel element.

Example 11

A modified version of the smoking article of Figure 9 was made 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 internal 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 assembled into 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 with cigarette paper. When smoked under FTC conditions, the smoking article 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 scorch.

Claims (95)

1. Cigarette-like smoking article with a mouth end (15) comprising a fuel element (10) comprising mainly carbon as such and having an ignited end and a rear end, and physically separate aerosol generating means (12; 38; 80; 30; 52, 54) comprising an aerosol-forming material and arranged between the ignited end of the fuel element and the mouth end, characterized in that this fuel element (10) has a length of less than 30 mm before smoking and is designed and arranged to burn throughout the smoking process in order to generate heat for volatilizing aerosol-forming material during the entire smoking process. 2. Cigarette-like smoking article with a mouth end (15) comprising a fuel element (10) with a density of at least 0.5 g/cm³, a lighting end and a rear end, and with physically separate aerosol generating means (12; 38; 80; 30; 52, 54) comprising an aerosol generating material and arranged between the lighting end of the fuel element and the mouth end, characterized in that this fuel element (10) has a length of less than 30 mm before smoking and is designed and arranged so that it burns throughout the smoking process in order to generate heat for volatilizing aerosol forming material during the entire smoking process. 3. Smoking article according to claim 1 or 2, wherein the fuel element (10) has at least one passage (16) extending in the longitudinal direction. 4. Smoking article according to one of claims 1 to 3, whose aerosol generating means (12; 38; 80; 30; 52, 54) comprise a thermally stable substrate (20) which supports the aerosol-forming material. 5. Smoking article according to one of claims 1 to 4, in which the aerosol generating means (12; 38; 30; 52, 54) are adjacent to the rear end of the fuel element (10) so that during the entire smoking process, heat and heated gases are supplied to the aerosol generating material from the fuel element. 6. Smoking article according to one of claims 1 to 5, in which the fuel element (10) is a pressed or extruded mass. 7. Smoking article according to one of claims 1 to 6, in which the aerosol generating means (12; 38; 80; 52, 54) contact the fuel element (10). 8. Smoking article according to one of claims 1 to 7, whose fuel element (10) has a tapered end to be ignited. 9. Smoking article according to one of claims 1 to 8, in which - in the longitudinal direction of the smoking article - the aerosol generating means (12; 38; 30; 52, 54) are arranged behind the fuel element (10). 10. Smoking article according to one of the preceding claims, in which the fuel element (10) is arranged at the end of the smoking article to be lit. 11. Smoking article according to one of claims 3 to 10, in which the fuel element (10) has a plurality of such passages (16). 12. Smoking article according to one of claims 3 to 11, in which at least one passage (10) has the shape of a hole. 13. Smoking article according to one of the preceding claims, in which the fuel element (10) before smoking has a length of approximately 20 mm or less. 14. A smoking article according to claim 13, wherein the fuel element (10) has a length of approximately 15 mm or less prior to smoking. 15. Smoking article according to one of the preceding claims, in which the fuel element (10) before smoking has a length of approximately 5 mm to 30 mm. 16. A smoking article according to claim 15, wherein the fuel element (10) has a length of approximately 5 mm to 20 mm prior to smoking. 17. A smoking article according to claim 16, wherein the fuel element (10) has a length of about 5 mm to about 15 mm prior to smoking. 18. Smoking article according to one of the preceding claims, in which the fuel element (10) has a diameter between about 3 mm and about 8 mm. 19. A smoking article according to claim 18, wherein the fuel element (10) has a diameter of about 4 mm to about 5 mm. 20. Smoking article according to claim 1, wherein the fuel element (10) has a density of at least 0.5 g/cm³. 21. A smoking article according to any preceding claim, wherein the fuel element (10) has a density in the range of about 0.5 g/cm³ to about 1.5 g/cm³. 22. A smoking article according to claim 21, wherein the fuel element (10) has a density of greater than about 0.7 g/cm³. 23. Smoking article according to one of the preceding claims, in which the fuel element (10) has a density of at least about 0.8 g/cm³. 24. Smoking article according to claim 2, wherein the fuel element (10) predominantly comprises carbon as such. 25. Smoking article according to one of the preceding claims, the fuel element (10) of which contains at least approximately 50% by weight of carbon as such. 26. Smoking article according to claim 25, whose fuel element (10) contains at least 60 wt.% to 80 wt.% carbon as such. 27. Smoking article according to claim 26, the fuel element (10) of which contains at least about 80% by weight of carbon as such. 28. Smoking article according to claim 27, the fuel element (10) of which contains at least about 85% by weight of carbon as such. 29. Smoking article according to one of the preceding claims, the fuel element (10) of which is substantially free of volatile organic material. 30. 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. 31. 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. 32. A smoking article according to claim 31, wherein the heat transfer member (87) contacts or overlaps at least a portion of the fuel element (10) and the aerosol generating means (30). 33. Smoking article according to claim 31 or 32, wherein the heat transfer member (87; 52) comprises at least a portion of the aerosol generating means (30; 54, 56). 34. Smoking article according to one of claims 31 to 33, in which the heat transfer member (99) is located at least partially within the fuel element (10). 35. Smoking article according to one of claims 31 to 34, wherein the heat transfer member (87) encloses a portion of the longitudinally extending outer periphery of the fuel element (10) and the aerosol generating means (30). 36. Smoking article according to one of claims 31 to 35, in which the heat transfer member is a heat-conducting container (52) for the aerosol generating means (54, 56). 37. Smoking article according to claim 36, wherein the end of the heat-conducting container (52) facing the fuel element contacts a rear part of the fuel element (10). 38. Smoking article according to one of claims 31 to 37, 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. 39. Smoking article according to one of claims 31 to 38, wherein the heat transfer member (87; 52) is a metallic member, preferably made of aluminum. 40. Smoking article according to one of claims 36 to 39, wherein the container (52) is a heat-conducting metallic tube. 41. A smoking article according to any one of claims 36 to 40, wherein the container (52) overlaps the rear portion of the fuel element (10), surrounds the aerosol generating means (54, 56) and allows the passage of air and the aerosol forming material. 42. Smoking article according to one of claims 31 to 41, wherein the heat transfer member comprises a conductive rod (99) embedded in at least a portion of the fuel element (10) and in a portion of the aerosol generating means (30). 43. Smoking article according to one of the preceding claims, further comprising an insulating member (86) which encloses at least a portion of the fuel element (10). 44. A smoking article according to any preceding claim, further comprising an insulating member (86) enclosing at least a portion of the aerosol generating means (52, 54, 56). 45. A smoking article according to claim 43 or 44, wherein the insulating member (86) is non-combustible. 46. Smoking article according to one of claims 43 to 45, the insulating member (86) of which is at least 0.5 mm thick. 47. A smoking article according to claim 46, wherein the insulating member (86) is approximately 1 mm to 2 mm thick. 48. Smoking article according to one of claims 43 to 47, the insulating member (86) of which comprises an air-permeable mass of inorganic fibers. 49. Smoking article according to one of claims 43 to 48, the insulating member (86) of which is elastic. 50. Smoking article according to claim 49, wherein the insulating member comprises an air-permeable, elastic sleeve (86) made of fibers. 51. A smoking article according to any one of claims 43 to 50, wherein the insulating member (86) has a thermal conductivity of less than about 0.005 g-cal/(sec) (cm²) (°C/cm). 52. A smoking article according to any one of claims 36 and 43 to 51, wherein the insulating member (86) surrounds at least a portion of the conductive container (52). 53. Smoking article according to one of claims 43 to 52, in which the insulating member (86) comprises a material which melts during use, 54. A smoking article according to any one of claims 43 to 53, wherein the insulating member (86) comprises a low temperature grade of glass fibers. 55. A smoking article according to claim 54, wherein the insulating member (86) comprises glass fibers having a softening point below about 650ºC. 56. Smoking article according to one of the preceding claims, in which a tobacco charge (56) is provided. 57. A smoking article according to claim 56, wherein the tobacco charge (56) is disposed between the rear end of the fuel element (10) and the mouth end (15) of the smoking article. 58. Smoking article according to one of the preceding claims, in which tobacco (56) is arranged between the aerosol generating means (54) and the mouth end (15) of the smoking article. 59. Smoking article according to claim 58, wherein the tobacco (56) is arranged at the rear end of the aerosol generating means (54). 60. Smoking article according to one of the preceding claims, which has a quantity of tobacco extract between the rear end of the fuel element (10) and the mouth end (15) of the smoking article. 61. 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). 62. 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). 63. Smoking article according to one of the preceding claims, in which the aerosol generating means (30) are adjacent to the fuel element (10). 64. 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 by thermal conduction substantially during the entire burning time of the fuel element. 65. Smoking article according to claim 64, in which the fuel element (10) and the aerosol generating means (30) are in conductive heat exchange with one another by contact between the aerosol generating means and a portion of the fuel element. 66. 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. 67. Smoking article according to claim 66, 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. 68. 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. 69. A smoking article according to claim 68, wherein the aerosol generating means (30; 54, 56) are loaded with 35 mg to 85 mg aerosol forming material. 70. 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. 71. 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. 72. A smoking article according to any preceding claim, the aerosol generating means (30; 54, 56) of which is loaded with sufficient aerosol forming material to cause the smoking article to deliver at least about 1.5 mg total of moist particles during the first three puffs under smoking conditions with puffs of 35 ml and 2 seconds duration, separated by smolders of 58 seconds duration. 73. 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 on average at least about 0.8 mg total moist particles per puff for at least 6 puffs under smoking conditions with 35 ml puffs of 2 seconds duration separated by smoldering periods of 58 seconds. 74. A smoking article according to claim 73, which delivers on average per puff at least about 0.8 mg of total moist particles under smoking conditions with 35 ml puffs of 2 seconds duration, separated by smoldering periods of 58 seconds, over at least 10 puffs. 75. Smoking article according to one of the preceding claims, in which the aerosol generating means (54, 56) are arranged in a container (52). 76. Smoking article according to claim 75, wherein the container (52) is bent at its mouth end. 77. Smoking article according to one of the preceding claims, the aerosol generating means (30; 54, 56) of which contain a tobacco extract. 78. 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 and the mouth end of the smoking article. 79. A smoking article according to any preceding claim, the components of which are selected and arranged so that the smoke produced by the smoking article 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. 80. A smoking article according to any one of the preceding claims, the components of which are selected and arranged so that the smoke produced by the smoking article, measured by the Ames test, does not exhibit mutagenic activities in the total amount of moist particles. 81. A smoking article according to any preceding claim, which has a diameter of approximately 8 mm or less. 82. A smoking article according to any preceding claim, which has the size and shape of a cigarette. 83. Smoking article according to one of the preceding claims, which additionally has a mouth end piece (45). 84. A smoking article according to claim 83, which comprises means (44) for delivering the aerosol forming material to the user, wherein said mouth end piece (45) and the aerosol delivery means (44) extend for more than half the length of the smoking article. 85. A smoking article according to any preceding claim, the components of which are selected and arranged to deliver a visible smoke-like aerosol. 86. A smoking article according to any preceding claim, which is adapted for use with a separate mouthpiece. 87. Smoking article according to one of the preceding claims, which further comprises means (52, 44; 87, 44) for conducting the gases of the fuel element (10) through the aerosol generating means (54, 56; 30) and to the mouthpiece (45). 88. Smoking article according to one of claims 4 to 87, whose thermally stable substrate (20) contains ceramic material. 89. Smoking article according to one of the preceding claims, the aerosol generating means (54) of which comprise a particulate substrate. 90. Smoking article according to one of the preceding claims, which further comprises a filter (45). 91. 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 to the aerosol generating means in order to volatilize or vaporize the aerosol forming material during the draw throughout the smoking process. 92. 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 to the aerosol generating means in order to keep the latter heated between puffs. 93. 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). 94. 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. 95. Smoking article according to one of claims 31 to 94, in which the heat transfer member (52, 87) is designed and arranged so that it transfers 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.