CN110602954A

CN110602954A - Aerosol-generating article with insulated heat source

Info

Publication number: CN110602954A
Application number: CN201880030186.1A
Authority: CN
Inventors: F·达克
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2017-05-31
Filing date: 2018-05-30
Publication date: 2019-12-20
Also published as: RU2019142656A; US20200196660A1; KR20200011941A; WO2018220082A1; JP2020521441A; EP3629778A1; AR111898A1; TW201904453A; RU2019142656A3; JP7414527B2; BR112019022734A2

Abstract

An aerosol-generating article (2) comprising an aerosol-forming substrate (4), a combustible heat source (3) and at least one layer of ceramic paper (5) circumscribing at least a portion of the length of the combustible heat source (3). The at least one layer of ceramic paper (5) comprises a cellulose derivative binder.

Description

Aerosol-generating article with insulated heat source

Technical Field

The present invention relates to an aerosol-generating article comprising an aerosol-forming substrate and a combustible heat source and a method for forming such an aerosol-generating article.

Background

Several aerosol-generating articles in which tobacco is heated rather than combusted have been proposed in the art. One purpose of such 'heated' aerosol-generating articles is to reduce harmful smoke constituents of the known type that are produced by combustion and thermal degradation of tobacco in combustible cigarettes. In one known type of heated aerosol-generating article, an aerosol is generated by transferring heat from a combustible heat source to an aerosol-forming substrate located adjacent the combustible heat source. During aerosol generation, volatile compounds are released from the aerosol-forming substrate by heat transfer from the combustible heat source and entrained in air drawn through the aerosol-generating article. As the released compound cools, the compound condenses to form an aerosol that is inhaled by the user.

The combustion temperature of a combustible heat source for use in a heated aerosol-generating article should not be so high as to cause combustion or thermal degradation of the aerosol-forming substrate during use of the heated aerosol-generating article. However, especially during early puffs, the combustion temperature of the combustible heat source should be high enough to generate sufficient heat to release sufficient volatile compounds from the aerosol-forming substrate to produce an acceptable aerosol.

Various combustible heat sources have been proposed in the art for use in heated aerosol-generating articles. The combustion temperature of a combustible heat source for use in a heated aerosol-generating article is typically between about 600 ℃ and 800 ℃.

It is known to wrap a barrier member around the periphery of a combustible heat source of a heated aerosol-generating article in order to reduce the surface temperature of the heated aerosol-generating article. However, it has been found that such a barrier member may reduce the temperature of the combustible heat source during combustion of the combustible heat source, potentially reducing the effect of the heat source heating the aerosol-forming substrate to generate the aerosol. This effect is particularly evident where the partition member extends substantially the length of the combustible heat source. Such spacer members may also inhibit continued combustion of the combustible heat sources such that the duration of combustion of the combustible heat sources is reduced.

It is desirable to provide an aerosol-generating article which has a reduced surface temperature close to the heat source, an acceptable appearance, and which can be assembled in a simple and reliable manner. It would also be desirable to provide an aerosol-generating article that generates an acceptable aerosol both during early puffs and during later puffs.

Disclosure of Invention

According to a first aspect of the invention there is provided an aerosol-generating article comprising an aerosol-forming substrate, a combustible heat source and at least one layer of ceramic paper surrounding at least a portion of the length of the combustible heat source. The at least one layer of ceramic paper comprises a cellulose derivative.

In use, the combustible heat source may be ignited by an external heat source, such as a lighter, and combustion may begin. The combustion heat source may heat the aerosol-forming substrate such that volatile compounds of the aerosol-forming substrate vaporise. When a user draws on the aerosol-generating article, air may be drawn into the aerosol-generating article and mixed with vapour from the heated aerosol-forming substrate to form an aerosol. The aerosol may be drawn out of the aerosol-generating article and delivered to a user for inhalation by the user.

The at least one layer of ceramic paper surrounding at least a portion of the length of the combustible heat source may insulate the combustible heat source. This may reduce the surface temperature of the aerosol-generating article at the combustible heat source. The at least one layer of ceramic paper may also allow sufficient air to pass through the layer such that combustion of the combustible heat source may be substantially unimpeded.

As used herein, the term 'paper' is used to describe a fibrous tissue pad or sheet. Typically, the paper described herein is made from a fibrous slurry pressed into a sheet or mat. The paper of the present invention may comprise woven fibers. However, the paper of the present invention typically includes non-woven fibers. The fibers of the paper of the present invention may be randomly interwoven. The paper described herein is typically thin. In other words, the thickness or depth of the fibrous mat or sheet is substantially less than other dimensions of the mat or sheet, such as the length and width of the mat or sheet. Generally, the paper described herein is flexible. In other words, the paper described herein may be bent or shaped so as to wrap around the circumference of the combustible heat source such that the paper surrounds at least a portion of the combustible heat source.

As used herein, the term 'ceramic paper' is used to describe paper comprising ceramic materials. In other words, the term "ceramic paper" is used to describe a thin mat or fibrous sheet comprising a ceramic material. As used herein, the terms 'ceramic paper' and 'ceramic fiber paper' are used interchangeably.

The ceramic paper of the present invention comprises fibers of a ceramic material. The ceramic paper may comprise woven fibers of ceramic material. The ceramic paper may comprise non-woven fibers of ceramic material. The ceramic paper may comprise a fibrous ceramic material comprising at least one of a ceramic fiber batt, and a ceramic fiber fleece. In some embodiments, the ceramic paper may include only ceramic material fibers. In other words, in some embodiments, the ceramic paper may not include fibers of non-ceramic materials.

The ceramic paper may comprise other forms of ceramic material, including particulate ceramic material. The ceramic paper may comprise more than one form of ceramic material, for example fibrous and particulate ceramic materials.

The ceramic material may comprise any suitable ceramic material. The ceramic material may comprise a crystalline ceramic material. The ceramic material may comprise a semi-crystalline ceramic material. The ceramic material may comprise an amorphous ceramic material. The ceramic material may be amorphous. The ceramic material may be semi-crystalline. The ceramic material may be crystalline.

As used herein, the term 'ceramic material' encompasses glass. As used herein, the term 'glass' is used to describe a material that exhibits a glass transition at a glass transition temperature. Generally, the term 'glass' is used herein to describe amorphous or amorphous solid materials. However, the term 'glass' also encompasses materials that include both crystalline and amorphous components. Glass materials that include both crystalline and amorphous components may be referred to as 'glass-ceramic' materials.

The characteristics of the glass material of the present invention can be determined by the glass forming method. As used herein, the term 'glass' encompasses glasses formed by any suitable method. Suitable methods of forming the glass include: melting and quenching; physical vapor deposition; solid state reactions, including thermochemical and mechanochemical reactions; liquid state reactions, such as sol-gel processes; irradiation of crystalline solids, e.g. radiation amorphization; and pressure amorphization (i.e., formation under high pressure action).

In some embodiments, the ceramic material may comprise glass. The ceramic material may be glass. The glass may be a glass-ceramic material. The ceramic paper may comprise glass fibers. The ceramic paper may comprise glass ceramic fibers.

In some embodiments, the ceramic material may not include glass. In other words, the ceramic material may comprise any ceramic material other than glass. The ceramic material may not be a glass material. The ceramic material may not include glass fibers. In these embodiments, the ceramic material generally comprises a crystalline ceramic material.

The ceramic material may include at least one of an oxide, a carbide, a boride, a nitride, and a silicide. For example, the ceramic material may comprise a metal oxide. The ceramic paper may comprise silicon dioxide (SiO)₂) Calcium oxide (CaO), magnesium oxide (MgO), and aluminum oxide (Al)₂O₃) And zirconium dioxide (ZrO)₂) All of which are understood as ceramic materials. For example, the ceramic paper may include at least one of an alkaline earth metal silicate wool, an alumina silicate wool, or a polycrystalline wool. The ceramic paper may include iron oxide (Fe)₂O₃) Potassium oxide (K)₂O), sodium oxide (Na)₂O), all of which are understood as ceramic materials.

The ceramic paper may include any suitable amount of fibrous material. The ceramic paper may include at least about 40 weight percent ceramic material; at least about 50 weight percent of a ceramic material; or at least about 60 weight percent of a ceramic material. The ceramic paper may include less than about 99.99 weight percent ceramic paper material; or less than about 95 weight percent ceramic material. For example, the ceramic paper may include between about 50 weight percent and about 99.99 weight percent ceramic material.

The ceramic paper may comprise a non-fibrous material. The non-fibrous material may comprise water.

At least one layer of ceramic material according to the invention comprises a cellulose derivative binder. In some ceramic papers, a binder is used to hold the ceramic material together. The provision of the binder may also improve the mechanical properties of the ceramic paper. For example, the binder may make the ceramic paper less brittle and more flexible. This may advantageously allow at least one layer of ceramic paper to be wrapped around at least a portion of the combustible heat source.

As used herein, the term "cellulose derivative binder" is used to describe a binder comprising a cellulose derivative. Specifically, the cellulose derivative binder may include a cellulose derivative formed by adding specific pendant groups to cellulose.

Suitable cellulose derivatives include, but are not limited to: carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), hydroxyethyl methyl cellulose (HEC), hydroxyethyl cellulose, cellulose acetate, cellulose esters, and cellulose ethers. Preferably, the cellulose derivative binder comprises carboxymethyl cellulose.

The cellulose derivative binder may be dispersed in a liquid, such as water, at a concentration of about 0.01 weight percent to about 20 weight percent.

It has been found that the use of ceramic paper comprising a cellulose derivative binder advantageously secures the ceramic fibres together and provides the advantageous mechanical properties described above. In addition, it has been found that the use of ceramic paper comprising cellulose derivative binder does not produce an unpleasant odour when the combustible heat source is ignited and burnt.

The at least one layer of ceramic paper may comprise any amount of cellulose derivative binder. The at least one layer of ceramic paper may comprise at least about 0.01 weight percent of a cellulose derivative binder, at least about 1 weight percent of a cellulose derivative binder, at least about 5 weight percent of a cellulose derivative binder, or at least about 10 weight percent of a cellulose derivative binder. In some embodiments, at least one layer of ceramic paper may comprise no more than or equal to about 40 weight percent cellulose derivative binder, no more than about 30 weight percent cellulose derivative binder, or no more than about 15 weight percent cellulose derivative binder. The at least one layer of ceramic paper may comprise about 0.01 weight percent to about 40 weight percent of the cellulose derivative binder. The ceramic paper may comprise a non-ceramic material. The non-ceramic material may comprise a polymeric material. The non-ceramic material may comprise an organic material. The non-ceramic material may comprise an inorganic material.

The ceramic paper may be further reinforced by additional means such as particle reinforcement. For example, carbon black particles may be used to reinforce ceramic paper. The ceramic paper may further comprise any other suitable ingredients including, but not limited to, titanium dioxide, aluminum trihydrate, and pigments that may comprise iron and manganese.

The ceramic paper can include any suitable amount of non-ceramic material. In some embodiments, the ceramic paper may include only ceramic material. In other words, in some embodiments, the ceramic paper may not include any non-ceramic materials. The ceramic paper may include about 0 weight percent non-ceramic material. The ceramic paper may include between 0 weight percent and about 25 weight percent of non-ceramic materials. The ceramic paper may include: at least about 0.5 weight percent of a non-ceramic material; at least about 2 weight percent of a non-ceramic material; at least about 10 weight percent of a non-ceramic material; at least about 20 weight percent of a non-ceramic material; at least about 30 weight percent of a non-ceramic material; at least about 40 weight percent of a non-ceramic material; or at least about 50 weight percent of a non-ceramic material. The ceramic paper may include less than about 40 weight percent non-ceramic materials; less than about 30 weight percent of a non-ceramic paper material; or less than about 15 weight percent of non-ceramic materials.

In some embodiments, the ceramic paper may include low biopersistence fibers. In some particular embodiments, the fibrous material of the ceramic paper may be comprised of low biopersistence fibers.

As used herein, the term "biopersistence" refers to the length of time that intact fibers remain in the lungs and pleura (chest cavity) of a human's respiratory system.

Suitable short-term tests for measuring biopersistence include short-term inhalation experiments. An exemplary short-term inhalation experiment involves exposing rodents to a known concentration of a given fiber type for 5 days per day, 6 hours per day, followed by periodic sacrifice to determine lung fiber load. Such a process is described in Bernstein, D.M., C.Morscheid, H. -G.Grimm, P.Thevenaz and U.Teichert.1996.evaluation of soluble fibers using the correlation biopersistence model, a non-fiber complex. innovation Toxicol.8(4): 345-. Suitable alternative short-term tests to measure biopersistence include intratracheal instillation experiments involving administering fibers in a known amount of saline to rodents via intratracheal instillation, and these rodents are periodically sacrificed to determine lung fiber load.

The results of the short-term inhalation method and the endotracheal infusion method can be expressed as a weighted clearance half-time (wt1/2) or the time required to clear 90% of the fibers from the lungs (T90).

Fibers can be considered to have "low biopersistence" or "low biopersistence" if short-term biopersistence testing by inhalation shows that fibers longer than 20 microns have a weighted half-life of 10 days or less, or short-term biopersistence testing by intratracheal instillation shows that fibers longer than 20 microns have a weighted half-life of 40 days or less, as described in the european commission directive 97/69/EC annotation Q on 12, 5 days 1997. If 2mg of fine suspension is infused into the trachea and the fibres are 5 μm in length, the fibres can also be considered as "low biomass" or "low biomechanical scaffold", less than 3 μm in diameter, with a length ratio exceeding 3: 1(WHO fiber) did not exceed 40 days, as described in the 10/26 th European Committee on 26 th quarter 1999/836/EC on 1999 in the European Committee on 26 nd quarter on the year of quarter 2, mineral products on 97/69/EC directive notified in Germany.

Materials with low biological persistence may be removed or cleared from the respiratory system of a person by a mechanism. One exemplary mechanism of material removal from the respiratory system is physical displacement, such as by mucociliary transport. Another exemplary mechanism for removing material from the respiratory system is chemical dissolution. A material may be considered "biosoluble" if its solubility in solvents of the respiratory system is sufficiently high.

In some embodiments, the ceramic paper may include biosoluble fibers. In some particular embodiments, the fibrous material of the ceramic paper may be comprised of biosoluble fibers.

As used herein, the term "biosoluble" is used to describe materials that are soluble in biological systems; in particular, it is used to describe materials that are soluble in the respiratory system of humans. The biosolubility of a material in the human respiratory system may be significantly different from the solubility of a material in water. As used herein, biosoluble fibers are considered to be low biopersistence fibers.

As used herein, a substance may be considered "biosoluble" if the in vitro static solubility test indicates that at least 0.1g of the substance is dissolved in 100ml of the solvent of the human respiratory system. Similarly, a substance may be considered to be bio-insoluble if static solubility testing indicates that less than 0.1g of the substance dissolves in 100ml of solvent of the human respiratory system.

A suitable in vitro static solubility test involves exposure of a sample of the substance to be tested to a suitable solvent at a temperature of 37 ℃ for 24 hours. After 24 hours, the solubility can be measured by determining the composition of the dissolution or the weight of the remaining sample. For example, elemental analysis using inductively coupled plasma spectroscopy of the dissolution solution can be used to calculate the total mass of the sample dissolved in the dissolution solution.

Suitable solvents for use as human respiratory solvent in the in vitro static solubility test include physiological saline solutions and alternatives to human respiratory solvents, such as the known Simulated Lung Fluid (SLF). Suitable SLFs are known to include an artificial lysozyme body fluid (ALF) at pH about 4.5, which is similar to the fluid that alveoli and interstitial macrophages in the lung would contact after phagocytosis by inhaled particles, and a Gamble solution at pH about 7.4, which is similar to interstitial fluid deep into the lung.

As used herein, a substance may also be considered biosoluble if the in vitro dynamic solubility test indicates that the dissolution rate constant of the substance in the solvent of the human respiratory system is at least 150 nanograms per square centimeter per hour (ng/cm2 · h).

Suitable in vitro dynamic solubility tests include slowly flowing a suitable solvent through a sample of the test substance and measuring the solubility of the fiber over time. To determine whether the solubility of the sample is uniform over a long period of time, the test is conducted for a long period of time, for example at least three weeks. In more detail, a suitable solvent is slowly pumped through a fiber sample that has been normalized to its surface area, so that fresh solution is always provided to the sample. A particularly suitable in vitro dynamic solubility test involves flowing a suitable solvent through the sample to be tested at a rate of 5ml per hour for 1000 hours at a temperature of 37 degrees celsius. The solution was collected and analyzed for the concentration of elements leached from the fiber sample. The solution is collected multiple times during the test, for example twice a week, to determine if the solubility of the sample is uniform or constant over time.

Solubility can be measured by determining the composition of the dissolution solution or the weight of the remaining sample. For example, elemental analysis using inductively coupled plasma spectroscopy of the dissolution solution can be used to calculate the total mass of the sample dissolved in the dissolution solution at specific time intervals. Since the surface area of the sample and the flow rate of the solvent are known, and the concentration of the leachate is determined from the solubility test, these values can be used to determine solubility by known methods. The dissolution rate can be expressed in nanograms per square centimeter per hour per square centimeter.

Suitable solvents for use as solvents in the in vitro dynamic solubility test for the human respiratory system include physiological saline solution and SLF, as described above for the in vitro static solubility test.

One particular suitable in vitro dynamic Solubility test is described in B.D.Law, W.B.Bunn, and T.W.Hesterberg (2008) Solubility of Polymeric Organic Fibers and Manual vitamins Fibers in the Gambles Solution, related Solubility, 2:4,321-339, DOI: 10.3109/08958379009145261.

The biosoluble material may be any suitable biosoluble material. Suitable biosoluble materials include alkaline earth silicate materials and high alumina low silica materials.

In some preferred embodiments, the fibrous material comprises alkaline earth silicate fibers. In some particularly preferred embodiments, the fibrous material consists essentially of alkaline earth silicate fibers. In some particularly preferred embodiments, the fibrous material consists of alkaline earth silicate fibers.

In some embodiments of the invention, the ceramic paper may comprise about 99.99 weight percent of a fibrous alkaline earth silicate material, such as alkaline earth silicate wool.

In some embodiments of the invention, the ceramic paper may comprise: between about 50 weight percent and about 99.99 weight percent of the fibrous alkaline earth silicate material.

In some embodiments of the invention, the ceramic paper may comprise between about 60 weight percent and about 70 weight percent silica; between about 15 weight percent and about 35 weight percent calcium oxide; between about 4 weight percent and about 20 weight percent magnesium oxide.

In some embodiments of the invention, the ceramic paper may comprise: less than about 40 weight percent alumina; less than about 10 weight percent organic material; and less than about 1 weight percent moisture.

The above composition refers to the weight percentage of the various components after the ceramic paper has been ignited.

Examples of ceramic papers comprising biosoluble ceramic fibers that are currently commercially available include:Fibre Paper、Fibre Flex Wrap、HT Fibre、plus Fibre andplus 332-E; all of these were purchased from Morgan Advanced Materials, plc. Binder-free ceramic papers are also suitable, for example Rescor 300BL from Final Advanced Materials, or binderless biosoluble fibrous papers from DL-Thermal. Some binder-free ceramic papers may be suitable, the binder-free ceramic papers comprisingAt least one of: a biosoluble fiber; low biopersistent fiber; a fiber comprising at least one of silica, calcium oxide, and magnesium oxide. Some binder-free ceramic papers comprising alkaline earth silicate fibers may be suitable.

In some embodiments, the ceramic paper may comprise one or more of biosoluble fibers and low-biopersistence fibers. Examples of suitable materials for at least one of biosolubility and low biopersistence include, but are not limited to, silica, calcium oxide, and magnesium oxide. Particularly suitable materials for at least one of biosolubility and low biopersistence include alkaline earth metal silicates.

The ceramic paper may have a low thermal conductivity. In other words, the ceramic paper can be a good insulator. For example, the ceramic paper may have a thermal conductivity between about 0.5 to 2W/mK at a temperature of about 23 ℃. This low thermal conductivity is observed especially in the case of ceramic papers comprising woven or non-woven fibrous ceramic materials. This may be due to the relatively open, highly porous ceramic paper structure comprising fibrous ceramic material, which reduces heat transfer by conduction.

The ceramic paper may have high air permeability. This may be due to a relatively open, highly porous structure. At least one layer of ceramic paper may be sufficiently air permeable to cause the combustible heat source to burn substantially unimpeded. For example, the at least one layer of ceramic paper may have a thickness of greater than about 4000 (cm)³/(min*cm²) Air permeability of (2).

At least one layer of ceramic paper surrounds at least a portion of the length of the combustible heat source. The at least one layer of ceramic paper of the present invention may surround substantially the entire length of the combustible heat source. This may enable the aerosol-generating article to benefit from the thermal insulation properties of the ceramic paper to reduce the surface temperature to close to the heat source during use and from the air permeability of the ceramic paper to enable sufficient ambient air to reach the combustible heat source for ignition and substantially unimpeded combustion of the combustible heat source.

Ceramic paper may have advantageous mechanical properties. For example, ceramic paper may be flexible and machinable due to the reinforcing effect of the ceramic material, especially the ceramic fibers, if present. The ceramic paper may have a machinability that facilitates forming a layer of ceramic paper that surrounds at least a portion of the length of the heat source.

As used herein, the term 'layer' is used to describe a body of material that substantially conforms to the shape of the combustible heat source. The at least one layer of ceramic paper may be any suitable type of layer arranged to surround the heat source. Suitable types of layers include, inter alia, wrappers and coatings. As used herein, the term 'coating' is used to describe a layer of material that covers and adheres to a heat source.

At least one layer of ceramic paper may be in direct contact with the combustible heat source. The at least one layer of ceramic paper may be spaced from the combustible heat source.

At least one layer of ceramic paper surrounds at least a portion of the length of the combustible heat source. For example, the at least one layer of ceramic paper may surround about half of the length of the combustible heat source. The at least one layer of ceramic paper may surround more than half of the length of the combustible heat source. The at least one layer of ceramic paper may surround from about 60% to about 100% of the length of the combustible heat source. The at least one layer of ceramic paper may surround at least about 70% of the length of the combustible heat source. The at least one layer of ceramic paper may surround at least about 80% of the length of the combustible heat source. The at least one layer of ceramic paper may surround at least about 90% of the length of the combustible heat source. The at least one layer of ceramic paper may substantially surround the length of the combustible heat source.

The at least one layer of ceramic paper may surround the entire length of the combustible heat source. As used herein, the term 'length' is used to describe the dimension of a component or part of an aerosol-generating article in the longitudinal direction of the aerosol-generating article.

The at least one layer of ceramic paper may surround about half the length of the aerosol-forming substrate. Advantageously, the at least one layer of ceramic paper surrounding the aerosol-forming substrate may reduce the surface temperature of the aerosol-generating article at the aerosol-forming substrate.

At least one layer of ceramic paper may surround the combustible heat source at the downstream end of the combustible heat source. This may advantageously reduce the surface temperature of the aerosol-generating article at the portion of the combustible heat source closest to the user during normal operation of the aerosol-generating article.

At least one layer of ceramic paper may surround the combustible heat source at the upstream end of the combustible heat source.

At least one layer of ceramic paper may surround the combustible heat sources at the upstream and downstream ends.

The uncovered portions of the combustible heat sources may be referred to herein as 'bare' portions. The at least one layer of ceramic paper of the present invention may be arranged to cover or surround the 'bare' or uncovered portion of the combustible heat source.

In some embodiments, at the upstream end, a portion of the combustible heat source may be surrounded by at least one additional layer. The at least one additional layer may be a cigarette paper layer. In these embodiments, the upstream portion of the combustible heat source is an exposed portion. In other words, the upstream portion of the combustible heat source is not covered by the at least one additional layer. In these embodiments, the at least one layer of ceramic paper may surround an upstream portion of the combustible heat source. The at least one layer of ceramic paper may surround the combustible heat source from the upstream end of the at least one additional layer surrounding the upstream portion of the combustible heat source to or around the downstream end of the combustible heat source. Thus, in these embodiments, the combustible heat source may be surrounded substantially along its length by combining at least one additional layer at the downstream end and at least one layer of ceramic paper at the upstream end. In some embodiments, the at least one layer of ceramic paper and the at least one additional layer may overlap along the length of the combustible heat source.

The combustible heat source, the aerosol-forming substrate and the at least one layer of ceramic paper may be configured to substantially prevent or inhibit the temperature of the aerosol-forming substrate from exceeding about 375 ℃ during combustion of the combustible heat source. For example, the combustible heat source, the aerosol-forming substrate and the at least one layer of ceramic paper may be shaped, dimensioned and arranged to substantially prevent or inhibit the temperature of the aerosol-forming substrate from exceeding about 375 ℃ during combustion of the combustible heat source. This may preserve the integrity of the aerosol-forming substrate. For example, if the aerosol-forming substrate comprises one or more aerosol-formers, the aerosol-former may undergo pyrolysis at a temperature above about 375 ℃. For example, at even higher temperatures, and where the aerosol-forming substrate comprises tobacco, the tobacco may burn.

The combustible heat source, the aerosol-forming substrate and the at least one layer of ceramic paper may be configured such that the temperature of the aerosol-forming substrate 2mm from the proximal face of the aerosol-forming substrate is at least about 100 ℃ for a period of at least about 6 minutes during combustion of the combustible heat source.

The at least one layer of ceramic paper may have any suitable thickness. Typically, at least one layer of ceramic paper is a thin layer. The at least one layer of ceramic paper may have a thickness of at least about 0.25 mm or at least about 0.5 mm. The at least one layer of ceramic paper may have a thickness of less than about 10 millimeters or less than about 5 millimeters. The at least one layer of ceramic paper may have a thickness between about 0.25 mm and about 10 mm or between about 0.5 mm and about 5 mm.

The at least one layer of ceramic paper may further comprise one or more air inlets, such as one or more perforations. The one or more air inlets may further increase the air permeability of the at least one layer of ceramic paper.

In some embodiments of the invention, the aerosol-generating article further comprises one or more air flow paths along which air may be drawn through the aerosol-generating article for inhalation by a user. When a user draws on the aerosol-generating article, air may be drawn into the aerosol-generating article along one or more airflow paths.

The at least one layer of ceramic paper may be isolated from the one or more airflow paths such that, in use, air drawn through the aerosol-generating article along the one or more airflow paths does not directly contact the at least one layer of ceramic paper.

In some embodiments, the at least one layer of ceramic paper may be spaced apart from the one or more airflow paths such that air drawn through the aerosol-generating article along the one or more airflow paths does not directly contact the at least one layer of ceramic paper.

In some embodiments, one or more portions of at least one layer of ceramic paper may be covered, coated, or encapsulated in a material that is substantially impermeable to fibers and particles. One or more portions of at least one layer of ceramic paper covered, coated or encapsulated in a substantially fibre and particle impermeable material may be positioned in proximity to air drawn through the aerosol-generating article along one or more airflow paths. The covering, coating or encapsulating may isolate air drawn through the aerosol-generating article along the one or more airflow paths from the fibers and particles of the at least one layer of ceramic paper.

In some embodiments, one or more portions of the at least one layer of ceramic paper may be overlaid in a layer of paper to isolate the at least one layer of ceramic paper from the one or more gas flow paths. The one layer of paper may be disposed on at least one of an inner surface of the at least one layer of ceramic paper and an outer surface of the at least one layer of ceramic paper. The layer of paper may be disposed on both the inner and outer surfaces of the at least one layer of ceramic paper. The paper layer may comprise laminated paper. The one ply of paper may be co-laminated with at least one ply of ceramic paper. The layer of paper may be disposed only on a portion of the at least one layer of ceramic paper adjacent to the airflow path.

At least one layer of ceramic paper may be substantially flame resistant. As used herein, the term 'flame resistant' refers to a material that remains substantially intact during ignition and combustion of the combustible heat source. The provision of at least one layer of fire resistant ceramic paper surrounding at least part of the length of the combustible heat source may advantageously prevent flames or fumes from escaping from the layer. This may substantially prevent or inhibit the release of undesirable emissions or odours from the layer during combustion of the combustible heat source.

In some embodiments of the invention, the aerosol-generating article further comprises one or more non-combustible substantially air-impermeable barriers between the combustible heat source and the aerosol-forming substrate. The one or more non-combustible, substantially air impermeable barriers between the combustible heat source and the aerosol-forming substrate isolate the combustible heat source from the one or more airflow paths such that, in use, air drawn through the aerosol-generating article along the one or more airflow paths does not directly contact the combustible heat source.

Aerosol-generating articles according to the invention comprise an aerosol-forming substrate. As used herein, the term 'aerosol-forming substrate' is used to describe a substrate capable of releasing volatile compounds upon heating, which may form an aerosol. The aerosol generated from the aerosol-forming substrate of the aerosol-generating article according to the present invention may be visible or invisible and may comprise vapour (e.g. fine particles of a substance in the gaseous state, which is typically a liquid or solid at room temperature) as well as gas and liquid droplets of condensed vapour.

The aerosol-forming substrate may be solid. The aerosol-forming substrate may be solid at room temperature.

The aerosol-forming substrate may comprise at least one aerosol-former and at least one material capable of emitting volatile compounds in response to heating.

The at least one aerosol-former may be any suitable known compound or mixture of compounds which, in use, promotes the formation of a dense and stable aerosol and which is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol-formers are well known in the art and include, for example, polyols, esters of polyols (glycerol monoacetate, glycerol diacetate, or glycerol triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (e.g., dimethyl dodecanedioate and dimethyl tetradecanedioate). Exemplary aerosol-formers for use in aerosol-generating articles according to the invention are polyols or mixtures thereof, such as triethylene glycol, 1, 3-butanediol and glycerol.

The material capable of emitting volatile compounds in response to heating may be a charge of plant-based material, such as a charge of homogenous plant-based material. For example, the aerosol-forming substrate may comprise one or more materials derived from plants including, but not limited to: tobacco; tea leaves, such as green tea; mint; laurel; eucalyptus; basil; sage; verbena; and tarragon. The plant-based material may include additives including, but not limited to, humectants, fragrances, binders, and mixtures thereof. The plant-based material may consist essentially of a tobacco material, optionally a homogenised tobacco material.

Aerosol-generating articles according to the invention may comprise an aerosol-forming substrate comprising nicotine. For example, aerosol-generating articles according to the present invention comprise an aerosol-forming substrate comprising tobacco.

The aerosol-forming substrate may be surrounded by a plug segment wrapper.

Aerosol-generating articles according to the invention comprise a combustible heat source arranged to heat an aerosol-forming substrate and isolated from one or more airflow paths.

The combustible heat source may comprise a body of combustible material. The body of combustible material may have a substantially constant diameter. The body of combustible material may have a constant diameter along its length. This may advantageously simplify the processes involved in manufacturing the combustible heat sources and the aerosol-generating articles. In some embodiments, the body of combustible material may form a generally circular cylindrical body having a substantially constant diameter along its length.

The combustible heat source may be a carbonaceous heat source. As used herein, the term 'carbonaceous' is used to describe combustible heat sources comprising carbon. Preferably, the combustible carbonaceous heat source for use in the aerosol-generating article according to the invention has a carbon content of at least about 35%, more preferably at least about 40%, most preferably at least about 45% by dry weight of the combustible heat source 30.

Combustible heat sources according to the invention may be combustible carbon-based heat sources. As used herein, the term 'carbon-based heat source' is used to describe a heat source consisting essentially of carbon.

Combustible carbon-based heat sources for use in aerosol-generating articles according to the invention may have a carbon content of at least about 50%, preferably at least about 60%, more preferably at least about 70%, most preferably at least about 80% by dry weight of the combustible carbon-based heat source.

The combustible heat source of the invention is isolated from one or more airflow paths through the aerosol-generating article. As used herein, the term 'airflow path' is used to describe the route along which air can be drawn through the aerosol-generating article for inhalation by a user. As used herein, the terms 'upstream' and 'downstream' are used to describe the relative direction and position of components of the aerosol-generating article with respect to the direction of air flow through the one or more airflow paths when the aerosol-generating article is drawn by a user.

Isolating the combustible heat source from the one or more airflow paths of the aerosol-generating article may substantially prevent or inhibit activation of combustion of the combustible heat source during smoking by a user. This may substantially prevent or inhibit a sudden increase in the temperature of the aerosol-forming substrate during smoking by the user. This may substantially prevent or inhibit combustion or pyrolysis of the aerosol-forming substrate under severe smoking conditions. This may substantially prevent or inhibit the composition of the aerosol generated by the aerosol-generating article from changing due to the user's smoking status.

Isolating the combustible heat source from the one or more airflow paths may also substantially prevent or inhibit combustion and decomposition products, as well as other materials formed during ignition and combustion of the combustible heat source, from entering the air drawn through the aerosol-generating article along the one or more airflow paths.

The isolated combustible heat sources of the invention may comprise plug-type heat sources. As used herein, the term 'plug-type' is used to describe a combustible heat source in which air drawn through the aerosol-generating article for inhalation by a user does not pass through an airflow channel along the combustible heat source. Thus, heat transfer between the blind combustible heat source and the aerosol-forming substrate occurs primarily by conductive heat transfer.

By not providing an airflow channel through the combustible heat source, convective heat transfer between the combustible heat source and the aerosol-forming substrate may be reduced or minimised. Reducing convective heat transfer between the combustible heat source and the aerosol-forming substrate may substantially prevent or inhibit a temperature excursion of the aerosol-forming substrate during user smoking. This may substantially prevent or inhibit combustion or pyrolysis of the aerosol-forming substrate under severe smoking conditions. This may substantially prevent or inhibit the composition of the aerosol generated by the aerosol-generating article from changing due to the user's smoking status. This may also substantially prevent or inhibit combustion and decomposition products, as well as other materials formed during ignition and combustion of the combustible heat source, from entering the air drawn through the aerosol-generating article along the one or more airflow paths.

The isolated combustible heat sources of the invention may comprise non-blind type heat sources. As used herein, the term 'non-occlusive' is used to describe a heat source in which air drawn through an aerosol-generating article for inhalation by a user passes through one or more airflow channels along the heat source. Thus, heat transfer between the non-blind combustible heat source and the aerosol-forming substrate may occur by conductive heat transfer and by convective heat transfer along the one or more airflow channels.

As used herein, the term 'airflow channel' is used to describe a channel extending along the length of the combustible heat source through which air may be drawn downstream for inhalation by a user. As such, the aerosol-generating article of the present invention may not comprise one or more air flow channels.

The one or more non-combustible substantially air-impermeable barriers between the combustible heat source and the aerosol-forming substrate may comprise a first barrier contiguous with one or both of the proximal end of the combustible heat source and the distal end of the aerosol-forming substrate. The first barrier may help to isolate the combustible heat source from the one or more airflow paths of the aerosol-generating article. The first barrier may reduce the maximum temperature to a temperature to which the aerosol-forming substrate is exposed during ignition or combustion of the combustible heat source, and may substantially prevent or inhibit thermal degradation or combustion of the aerosol-forming substrate during use of the aerosol-generating article.

As used herein, the term 'non-combustible' is used to describe a material which is substantially non-combustible at the temperature reached by the combustible heat source during combustion or ignition thereof.

As used herein, the term 'air impermeable' is used to describe a material that substantially prevents or inhibits the passage of air therethrough.

The first barrier layer may abut one or both of a proximal end of the combustible heat source and a distal end of the aerosol-forming substrate. The first barrier may be bonded or otherwise attached to one or both of the proximal end of the combustible heat source and the distal end of the aerosol-forming substrate.

The first barrier may comprise a first barrier coating provided on the proximal face of the combustible heat source. In such embodiments, the first barrier may comprise a first barrier coating provided on at least substantially the entire proximal face of the combustible heat source. The first barrier may comprise a first barrier coating provided on the entire proximal face of the combustible heat source. The first barrier coating may be formed and applied to the proximal face of the combustible heat source by any suitable method, for example as described in WO-a 1-2013120855.

The first barrier may have a low thermal conductivity or a high thermal conductivity depending on the desired characteristics and performance of the aerosol-generating article. In certain embodiments, the first barrier may have a thermal conductivity between about 0.1W/m.k and about 200W/m.k.

The thickness of the first barrier may be suitably adjusted to achieve good aerosol-generating performance. In certain embodiments, the thickness of the first barrier may be between about 10 microns and about 500 microns.

The first barrier may be formed from one or more suitable materials that are substantially thermally stable and non-combustible at the temperatures reached by the combustible heat source during ignition and combustion. Suitable materials are known in the art and include, but are not limited to, clays (e.g., bentonite and kaolinite), glasses, minerals, ceramic materials, resins, metals, and combinations thereof.

The materials that can form the first barrier include clay and glass. Further materials from which the first barrier layer may be formed include copper, aluminum, stainless steel, alloys, aluminum oxide (Al)₂O₃) Resin and mineral glues.

Where the first barrier comprises a metal or alloy, for example copper, aluminium, stainless steel, the first barrier coating may advantageously act as a thermal connection between the combustible heat source and the aerosol-forming substrate. This may improve conductive heat transfer from the combustible heat source to the aerosol-forming substrate.

The aerosol-generating article may further comprise one or more air inlets downstream of the proximal end of the combustible heat source. In some embodiments, the one or more air inlets are between the proximal end of the combustible heat source and the proximal end of the aerosol-generating article. The one or more air inlets may be arranged such that air may be drawn into the one or more airflow paths of the aerosol-generating article through the one or more air inlets without being drawn through the combustible heat source. This may substantially prevent or inhibit a temperature excursion of the aerosol-forming substrate during smoking by a user.

The one or more air inlets may comprise any suitable air inlet through which air may be drawn into the aerosol-generating article. For example, suitable air inlets include holes, slits, slots, or other apertures. The number, shape, size and arrangement of the air inlets may be suitably adjusted to achieve good aerosol-generating performance.

One or more air inlets may be arranged at the aerosol-forming substrate. The one or more air inlets may be arranged between the distal end of the aerosol-forming substrate and the proximal end of the aerosol-forming substrate. Where the one or more air inlets are arranged at the aerosol-forming substrate and the aerosol-forming substrate comprises a filter segment package, the filter segment package may have one or more openings to allow air to enter into the aerosol-forming substrate. The one or more openings may be slits, slots or other suitable apertures through which air may be drawn into the aerosol-forming substrate. The number, shape, size and arrangement of the openings may be suitably adjusted to achieve good aerosol-generating performance.

The combustible heat source may comprise one or more airflow channels. In other words, the combustible heat source may be a non-blind type heat source. One or more airflow channels may extend along the length of the combustible heat source. The one or more air flow channels may form part of one or more air flow paths of the aerosol-generating article.

Where the combustible heat source comprises one or more air flow channels in the aerosol-generating article, the one or more non-combustible substantially air impermeable barriers between the combustible heat source and the aerosol-forming substrate may further comprise a second barrier between the combustible heat source and the one or more air flow channels of the combustible heat source.

The second barrier may help to isolate the combustible heat source from the one or more airflow paths of the aerosol-generating article. The second barrier may reduce the maximum temperature to which the aerosol-forming substrate is exposed during ignition or combustion of the combustible heat source, and thus help avoid or reduce thermal degradation or combustion of the aerosol-forming substrate during use of the aerosol-generating article.

The second barrier may be bonded or otherwise attached to the combustible heat source.

The second barrier may include a second barrier coating disposed on an inner surface of the one or more airflow channels. The second barrier may comprise a second barrier coating provided on at least substantially the entire inner surface of the one or more gas flow passages. The second barrier may comprise a second barrier coating provided on the entire inner surface of the one or more gas flow channels.

The second barrier coating may be provided by inserting a liner into one or more of the airflow channels. For example, where the one or more airflow paths comprise one or more airflow channels extending through the interior of the combustible heat source, non-combustible substantially air impermeable hollow tubes may be inserted into each of the one or more airflow channels.

The second barrier may advantageously substantially prevent or inhibit combustion and decomposition products formed during ignition and combustion of the combustible heat source of the aerosol-generating article according to the invention from entering air drawn downstream along the one or more airflow channels.

The second barrier may have a low thermal conductivity or a high thermal conductivity depending on the desired characteristics and performance of the aerosol-generating article. The second barrier may have a low thermal conductivity.

The thickness of the second barrier may be suitably adjusted to achieve good aerosol-generating performance. In certain embodiments, the thickness of the second barrier may be between about 30 microns and about 200 microns. In embodiments, the thickness of the second barrier is between about 30 microns and about 100 microns.

The second barrier may be formed from one or more suitable materials that are substantially thermally stable and non-combustible at the temperatures reached by the combustible heat source during ignition and combustion. Suitable materials are known in the art and include, but are not limited to, for example: clay; metal oxides such as iron oxide, alumina, titania, silica-alumina, zirconia, and ceria; a zeolite; zirconium phosphate; and other ceramic materials, or combinations thereof.

Materials that can form the second barrier include clay, glass, aluminum, iron oxide, and combinations thereof. If desired, a catalytic component, such as a component that promotes the oxidation of carbon monoxide to carbon dioxide, may be incorporated into the second barrier. Suitable catalytic components include, but are not limited to, for example, platinum, palladium, transition metals, and oxides thereof.

Where the aerosol-generating article according to the invention comprises a first barrier between the downstream end of the combustible heat source and the upstream end of the aerosol-forming substrate and a second barrier between the combustible heat source and the one or more airflow channels along the combustible heat source, the second barrier may be formed from the same or different material or materials as the first barrier.

Where the second barrier comprises A second barrier coating provided on the inner surface of the one or more gas flow channels, the second barrier coating may be applied to the inner surface of the one or more gas flow channels by any suitable method, for example as described in US-A-5,040,551 and WO-A1-2013120855.

The aerosol-generating article may further comprise one or more additional layers surrounding at least the proximal portion of the combustible heat source and the distal portion of the aerosol-forming substrate. The one or more additional layers may include at least one of: a heat conducting element to transfer heat from the combustible heat source to the aerosol-forming substrate; and a layer of cigarette paper.

The heat-conducting element may surround only a distal portion of the aerosol-forming substrate. The heat-conducting element may substantially surround the length of the aerosol-forming substrate. The heat conducting element may be in direct contact with at least one of the combustible heat source and the aerosol-forming substrate. The heat conducting element may not be in direct contact with either of the combustible heat source and the aerosol-forming substrate.

The heat-conducting element may provide a thermal connection between the combustible heat source and the aerosol-forming substrate. The thermally conductive element may be substantially flame resistant.

Suitable thermally conductive elements may include: metal foil wrapping paper or metal alloy foil wrapping paper. The metal foil packaging material may comprise: aluminum foil packaging material, steel foil packaging material, iron foil packaging material and copper foil packaging material. The thermally conductive element may comprise an aluminium tube.

The length of the proximal portion of the combustible heat source surrounded by the heat conducting element may be between about 2 millimetres and about 8 millimetres or between about 3 millimetres and about 5 millimetres.

The length of the distal portion of the combustible heat source not surrounded by the heat conducting element may be between about 4 millimetres and about 15 millimetres or between about 4 millimetres and about 8 millimetres.

The layer of cigarette paper may surround at least a proximal portion of the combustible heat source, the length of the aerosol-forming substrate and any other components of the aerosol-generating article arranged in proximity to the aerosol-forming substrate. The layer of cigarette paper may substantially surround the length of the combustible heat source. Where the layer of plugwrap substantially surrounds the length of the combustible heat source, the layer of plugwrap may have ventilation apertures, such as perforations, holes or slits, at the combustible heat source to enable air to pass through the layer of plugwrap to the combustible heat source. The number, shape, size and position of the openings may be suitably adjusted to achieve good aerosol-generating performance. The layer of cigarette paper may be wrapped tightly around the combustible heat source and the aerosol-forming substrate such that the layer of cigarette paper grips and secures the combustible heat source and the aerosol-forming substrate when the aerosol-generating article is assembled.

The at least one layer of ceramic paper may be the radially outer layer. Where the aerosol-generating article comprises one or more additional layers, the radially outer layer of ceramic paper may overlie at least a portion of the one or more additional layers. In other words, one or more additional layers may be arranged between the combustible heat sources and the at least one layer of ceramic paper. For example, where the aerosol-generating article comprises an additional layer comprising a heat-conducting element, the heat-conducting element may be a radially inner layer and the at least one layer of ceramic paper may be a radially outer layer, thereby surrounding at least a portion of the heat-conducting element.

As used herein, the terms 'radially outward' and 'radially inward' are used to indicate the relative distance of components of an aerosol-generating article from the longitudinal axis of the aerosol-generating article. As used herein, the term 'radial' is used to describe a direction perpendicular to the longitudinal axis of the aerosol-generating article, which extends in a direction between the proximal and distal ends of the aerosol-generating article.

The one or more additional layers may be radially outer layers. The one or more additional layers may overlie at least a portion of the at least one layer of ceramic paper.

The at least one layer of ceramic paper may be fastened or attached to one or more other components or portions of the aerosol-generating article. The at least one layer of ceramic paper may be secured to any suitable component of the aerosol-generating article. For example, the at least one layer of ceramic paper may be secured to at least one of the combustible heat source, the aerosol-forming substrate and the one or more additional layers. The at least one layer of ceramic paper may be secured to one or more components of the aerosol-generating article by any suitable means. At least one layer of ceramic paper may be secured using an adhesive. Suitable adhesives, such as silicate glues, may exhibit high temperature resistance. Where the one or more additional layers are radially outer layers, the one or more additional layers may be tightly wrapped around at least a portion of the at least one layer of ceramic paper.

In some embodiments, the at least one layer of ceramic paper may be integral with the combustible heat source. As used herein, the term 'integral' is used to describe a layer which is in direct contact with and adhered to the combustible heat source without the aid of an external adhesive or other intermediate connecting material.

In some embodiments, the at least one layer of ceramic paper may be formed from a strip of ceramic paper having opposing ends. The ceramic paper strip may be wrapped around the combustible heat source such that opposite ends of the strip overlap. The overlapping opposite ends of the strip may be secured together using adhesive or any other suitable means. In this way at least one layer of ceramic paper may be secured to the combustible heat source.

In some embodiments, an intermediate layer may be disposed between the at least one layer of ceramic paper and at least one of the combustible heat source, the aerosol-forming substrate and the one or more additional layers. The intermediate layer may be adjacent to at least one layer of ceramic paper. The intermediate layer may contact at least one layer of ceramic paper. The intermediate layer may be arranged radially inwardly of the at least one layer of ceramic paper.

The intermediate layer may be an adhesive layer. The adhesive layer may comprise any suitable adhesive. Suitable adhesives, such as silicate glues, may exhibit high temperature resistance. The adhesive layer may be arranged between the at least one layer of ceramic paper and the combustible heat source and may attach the at least one layer of ceramic paper to the combustible heat source. The adhesive layer may be disposed between the at least one layer of ceramic paper and the one or more additional layers and may attach the at least one layer of ceramic paper to the one or more additional layers. The adhesive layer may be arranged between the at least one layer of ceramic paper and the aerosol-forming substrate and may attach the at least one layer of ceramic paper to the aerosol-forming substrate.

In some embodiments, the at least one layer of ceramic paper may be formed from a strip of ceramic paper having opposing ends. The ceramic paper strip may be wrapped around the combustible heat source such that the opposite ends of the strip abut and do not overlap. An adhesive layer may be provided on the side of the strip facing the combustible heat source at least at the opposite end of the strip. The adhesive layer may secure the ceramic paper strip to the combustible heat source at least at opposite ends of the strip.

The aerosol-generating article may comprise a heat-conducting component arranged between the combustible heat source and the aerosol-forming substrate. The thermally conductive member may be the first barrier described above. The aerosol-generating article may comprise a thermally conductive component and a first barrier. The heat conducting member may comprise a similar material as the heat conducting element. The aerosol-generating article may comprise a thermally conductive component and a thermally conductive element. Providing at least one of a heat-conducting element and a heat-conducting member may facilitate conductive heat transfer between the combustible heat source and the aerosol-forming substrate.

The aerosol-generating article may also comprise any other suitable component. For example, the aerosol-generating article may comprise at least one of: a transfer element; an aerosol-cooling element; a spacer element; and a mouthpiece. One or more further components may be arranged coaxially with the combustible heat source and the aerosol-forming substrate. One or more further components may be arranged adjacent to the aerosol-forming substrate. The one or more further components may be arranged in any suitable order. The aerosol-generating article may further comprise: a transfer element adjacent a proximal end of the aerosol-forming substrate; an aerosol-cooling element adjacent the proximal end of the transfer element; a spacer element adjacent to the proximal end of the aerosol-cooling element; and a mouthpiece adjacent the proximal end of the spacing element.

As used herein, the terms 'proximal' and 'distal' are used to describe the relative positions of components or parts of components of aerosol-generating articles according to the invention. The proximal end of the component of the aerosol-generating article is the end of the component closest to the mouth end of the aerosol-generating article, and the distal end of the component of the aerosol-generating article is the end of the component furthest from the mouth end of the aerosol-generating article. Typically, the combustible heat source is arranged at a distal end of the aerosol-generating article.

According to a second aspect of the invention, there is provided a method of forming an aerosol-generating article according to the first aspect of the invention. The method comprises the following steps: arranging a combustible heat source to heat the aerosol-forming substrate; and surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper comprising a cellulose derivative binder.

In some embodiments, the step of surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper may comprise: providing a ceramic paper strip having opposite ends comprising a cellulose derivative binder; wrapping the strip around the combustible heat source such that the combustible heat source is surrounded by at least one layer of ceramic paper; overlapping opposite ends of the strip; and fastening the overlapping ends together to fasten the at least one layer of ceramic paper to the combustible heat source.

The overlapping ends of the ceramic paper strips may be secured together using any suitable means. For example, adhesive may be used to secure the overlapping ends of the ceramic paper strips together. Suitable adhesives should be high temperature resistant and include silica gels.

In some embodiments, the step of surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper may comprise: providing a banded ceramic paper having opposite ends comprising a cellulose derivative binder; applying an adhesive layer to one side of the strip at least at each of the opposite ends; arranging the strip with the adhesive layer facing the combustible heat source; wrapping the strip around the combustible heat source such that at least a portion of the length of the combustible heat source is surrounded by at least one layer of ceramic paper; abutting opposite ends of the strip without overlapping the opposite ends; and securing the strip to the combustible heat source using the adhesive layer.

In some embodiments, at least one layer of ceramic paper may be laminated with additional layers, such as a layer of cigarette paper. The at least one layer of ceramic paper may be laminated with the additional layer prior to application of the at least one layer of ceramic paper to the combustible heat source. A co-laminated paper strip comprising at least one layer of ceramic paper and an additional layer may be wrapped around the combustible heat source in the same manner as the ceramic paper strip. In some embodiments, the co-laminated paper may be arranged such that the at least one layer of ceramic paper faces the combustible heat source. In other words, the at least one layer of ceramic paper may be arranged radially inward of the additional layer. In some embodiments, the co-laminated paper may be arranged such that the additional layer faces the combustible heat source.

Although the invention relates to ceramic paper, the cellulose derivative binder may be used as a binder in a further layer, the binder in the further layer being used to surround at least a portion of the length of the combustible heat source of the aerosol-generating article. The cellulose derivative binder may be used in any layer of fibrous material. The cellulose derivative binder may be used in a layer of fibrous material comprising ceramic fibres.

A cellulose derivative binder may be used in the fiber-reinforced aerogel layer.

As used herein, the term "aerogel" is used to describe open-cell foams. The aerogel can be a mesoporous material. The term 'mesoporous material' refers to a material containing pores ranging in diameter from about 2 nanometers to about 50 nanometers. The aerogel can include a network of interconnected structures, which can be nanostructures. The aerogel can exhibit a porosity of about 50% or more. The aerogel can exhibit a porosity of about 90% or more. Aerogels can be formed by removing the liquid component from a conventional gel. Conventional gels are understood to mean semi-solid colloidal suspensions of solids dispersed in a liquid.

Aerogels generally have very low thermal conductivity. Without wishing to be bound by theory, conductive heat transfer is inhibited in aerogels due to their high porosity, while convective heat transfer is inhibited in aerogels due to the small diameter of the pores. The small diameter of the pores restricts the flow of air through the aerogel.

As used herein, the term 'fiber reinforced aerogel' refers to a composite material comprising an aerogel matrix reinforced with a fibrous material.

Drawings

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 shows a schematic representation of a first embodiment of an aerosol-generating article comprising a plugged combustible heat source according to the invention;

figure 2 shows a temperature profile of an aerosol-generating article similar to that shown in figure 1 at a first position in the article;

figure 3 shows a temperature profile of an aerosol-generating article similar to that shown in figure 1 at a second location in the article;

figure 4 shows a temperature profile of an aerosol-generating article similar to that shown in figure 1 at a third position in the article;

FIG. 5 shows a temperature profile at a third position of an aerosol-generating article similar to that shown in FIG. 1, wherein one of the aerosol-generating articles comprises a ceramic paper having biosoluble alkaline earth silicate fibers and

figure 6 shows a schematic representation of a second embodiment of an aerosol-generating article comprising a non-blind combustible heat source according to the invention.

Detailed Description

Figure 1 shows a schematic view of an aerosol-generating article 2. The aerosol-generating article 2 comprises a combustible heat source 3. The combustible heat sources 3 comprise substantially circular cylindrical bodies of carbonaceous material of about 10 millimetres in length. The combustible heat source 3 is a plug-type heat source. In other words, the combustible heat source 3 does not include any air channels extending therethrough.

The aerosol-generating article 2 further comprises an aerosol-forming substrate 4. An aerosol-forming substrate 4 is arranged at the proximal end of the combustible heat source 3. The aerosol-forming substrate 4 comprises a substantially circular cylindrical filter segment of tobacco material 18 surrounded by a filter segment wrapper 19.

A non-combustible, substantially air impermeable, first barrier 6 is arranged between the proximal end of the combustible heat source 3 and the distal end of the aerosol-forming substrate 4. The first barrier 6 comprises a disc of aluminium foil. The first barrier 6 also forms a heat conducting member between the combustible heat source 3 and the aerosol-forming substrate 4 to conduct heat from the proximal face of the combustible heat source 3 to the distal face of the aerosol-forming substrate 4.

The heat-conducting element 9 surrounds a proximal portion of the combustible heat source 3 and a distal portion of the aerosol-forming substrate 4. The heat conducting element 9 comprises an aluminium foil tube. The heat conducting element 9 is in direct contact with the proximal portion of the combustible heat source 3 and the plug wrap 19 of the aerosol-forming substrate 4.

The aerosol-generating article 2 also comprises various other components arranged in proximity to the aerosol-forming substrate 4, including: a delivery element 11 arranged at a proximal end of the aerosol-forming substrate 4; an aerosol-cooling element 12 arranged at the proximal end of the transfer element 11; a spacer element 13 arranged at a proximal end of the aerosol-cooling element 11; and a mouthpiece 10 arranged at the proximal end of the spacer element 13.

The components of the aerosol-generating article 2 are wrapped in a layer of cigarette paper 7. The cigarette paper layer 7 surrounds the heat-conducting element 9 but does not extend beyond the distal end of the heat-conducting element 9 on the distal portion of the combustible heat source 3.

According to the invention, the aerosol-generating article 2 further comprises a layer of ceramic paper 5. The layer of ceramic paper 5 substantially surrounds the length of the combustible heat source 3, the distal portion of the layer of cigarette paper 7, the heat-conducting element 9 and the aerosol-forming substrate 4. In other words, the layer of ceramic paper 5 is the radially outer layer at the distal end of the aerosol-generating article 2.

The layer of ceramic paper 5 comprises between about 60 weight percent and about 70 weight percent silica; between about 16 weight percent and about 22 weight percent calcium oxide; and between about 12 weight percent and about 19 weight percent magnesium oxide. The layer of ceramic paper 5 also comprises alumina. The layer of ceramic paper 5 also comprises a cellulose derivative binder. The cellulose derivative binder comprised CMC dispersed in water at a concentration of 8 weight percent.

A plurality of air inlets 8 are arranged at the aerosol-forming substrate 4 to allow ambient air to be drawn into the aerosol-generating article 2. The air inlet 8 comprises a plurality of perforations through the cigarette paper layer 7 and the underlying filter segment wrapper 19 surrounding the aerosol-forming substrate 4. The air inlet 8 is arranged between the distal and proximal faces of the aerosol-forming substrate 4.

When a user draws on the mouthpiece 10 of the aerosol-generating article 2, ambient air may be drawn into the aerosol-generating article 2 through the air inlet 8. Air drawn into the aerosol-generating article 2 may flow along the airflow path of the aerosol-generating article 2, from the air inlet 8, through the aerosol-forming substrate 4, the transfer element 11, the cooling element 12 and the spacing element 13 to the mouthpiece 10 and out of the mouthpiece 10 for inhalation by a user. The general direction of airflow through the aerosol-generating article 2 is indicated by the arrows.

In use, a user may ignite the combustible heat source 3 by exposing the combustible heat source 3 to an external heat source such as a lighter. The combustible heat source 3 may ignite and burn and heat may be transferred from the combustible heat source 3 to the aerosol-forming substrate 4 by conduction through the heat-conducting member 6 and the heat-conducting element 9. The volatile components of the heated aerosol-forming substrate 4 may be vaporised. A user may draw the mouthpiece 10 of the aerosol-generating article 2, drawing ambient air into the airflow path of the aerosol-generating article 2 through the air inlet 8. Vapour from the heated aerosol-forming substrate 4 may be entrained in the air drawn through the aerosol-forming substrate 4 and may be drawn together with the air towards the mouthpiece 10. As the vapor is drawn toward the mouthpiece 10, the vapor may cool to form an aerosol. The aerosol may be drawn from the mouthpiece 10 and delivered to the user for inhalation.

It will be appreciated that the substantially air impermeable first barrier 6 inhibits air being drawn through the combustible heat source 3 and into the aerosol-forming substrate 4. Thereby, the first barrier 6 substantially isolates the airflow path of the aerosol-generating article 2 from the combustible heat source 3.

In this embodiment, the layer of ceramic paper 5 extends over a tiny portion of the distal end of the aerosol-forming substrate 4. Thus, the layer of ceramic paper 5 is spaced from the air inlet 8. This spacing substantially isolates the layer of ceramic paper 5 from the air inlet 8 so that air drawn through the airflow path of the aerosol-generating article 2 does not contact the layer of ceramic paper 5.

It will be appreciated that in some embodiments, the layer of ceramic paper may be in close proximity to the air inlet. In these embodiments, the portion of the layer of ceramic paper that is in close proximity to the air inlet may be coated with a material that is substantially impermeable to fibers and particles. This may substantially isolate the portion of the layer of ceramic paper that is in close proximity to the air inlet such that air drawn through the airflow path of the aerosol-generating article does not contact the layer of ceramic paper.

Experimental data is collected to determine the temperature of a combustible heat source and an aerosol-forming substrate of various aerosol-generating articles similar to the aerosol-generating article 2 shown in figure 1 during combustion of the combustible heat source. Each aerosol-generating article tested comprises a layer of a different material substantially surrounding the length of the combustible heat source. In the experiment, holes 2mm deep were formed in the aerosol-generating article; in which two holes are formed at the position T shown in FIG. 1₁And T₂In the combustible heat source, a hole is formed in

Position T shown in FIG. 1₃In the aerosol-forming substrate. A thermocouple was inserted into each hole so that the temperature at each location could be measured. In particular, the experimental data collected for the aerosol-generating article comprises a layer of ceramic paper substantially surrounding the length of the combustible heat source and no layer of material substantially surrounding the length of the combustible heat source. Figures 2 to 4 show graphs of experimental measurements of temperature over time at three different locations of various aerosol-generating articles.

Figure 2 shows the temperature measured at a location 2 millimetres from the distal end of the combustible heat source corresponding to the location T shown in figure 1₁. In other words, figure 2 shows the temperature at the distal end of the combustible heat source.

Figure 3 shows the temperature measured at a location 5 millimetres from the distal end of the combustible heat source corresponding to the location T shown in figure 1₂. In other words, figure 3 shows along about half of the length of the combustible heat sourceAnd (3) temperature.

Figure 4 shows the temperature measured at a location 11 millimetres from the distal end of the combustible heat source corresponding to location T in figure 1₃. In other words, figure 4 shows the temperature at the distal end of the aerosol-forming substrate.

All temperature profiles were measured using an electronic temperature probe that was inserted approximately 2mm deep into the relevant components of the aerosol-generating article.

In figures 2, 3 and 4, the "SMAR" line labelled 20 shows the temperature profile of an aerosol-generating article having a "bare" combustible heat source. In other words, the "SMAR" line 22 shows the temperature profile of an aerosol-generating article without a layer of material substantially surrounding the length of the combustible heat source.

In figures 2, 3 and 4, the line "ceramic paper 1" labelled 21 shows the temperature profile of an aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source. The length of ceramic paper substantially surrounding the combustible heat source in the "ceramic paper 1" test was purchased from Morgan Advanced Materials, plcPlus Fibre。

In figures 2, 3 and 4, the line "ceramic paper 2" labelled 22 shows the temperature profile of an aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source. The length of Ceramic Paper substantially surrounding the combustible heat source in the "Ceramic Paper 2" test was CFP Ceramic fiber Paper available from Ningbo fire Thermal Insulation & Sealing co.

In figures 2, 3 and 4, the "cellophane" line labelled 23 shows the temperature profile of an aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source. The length of ceramic paper substantially surrounding the combustible heat source in the "glassine" test is ceramic paper comprising glass fibres.

It is desirable for an aerosol-generating article having a layer of material substantially surrounding the length of the aerosol-generating article to exhibit a temperature profile substantially similar to or exceeding the temperature profile 20 of an aerosol-generating article having a bare combustible heat source without a layer of material substantially surrounding the length of the combustible heat source. Where the combustible heat source exhibits a temperature similar to or higher than a bare combustible heat source, this indicates that the layer of material substantially surrounding the length of the combustible heat source does not substantially inhibit combustion of the combustible heat source.

Surprisingly, as shown in figures 2, 3 and 4, the temperature profile 21, 22, 23 of the aerosol-generating article with the layer of ceramic paper substantially surrounding the length of the combustible heat source is substantially similar to the temperature profile 20 of the aerosol-generating article without the layer of material substantially surrounding the length of the combustible heat source at all three test positions of the aerosol-generating article for the majority of the combustion time of the combustible heat source. Furthermore, over some period of time during the aerosol-generating experience, the temperature profiles 21 and 22 of the aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source actually exceed the temperature profile 20 of the aerosol-generating article not having a layer of material substantially surrounding the length of the combustible heat source.

This unexpected result indicates that providing at least one layer of ceramic paper substantially surrounding the length of the combustible heat source advantageously does not substantially impede combustion of the combustible heat source. Indeed, providing the layer of ceramic paper may increase the temperature of the combustible heat sources over a period of time during combustion of the combustible heat sources.

Figure 5 shows a graph of further experimental data collected for three specific aerosol-generating articles as described above. Similar to figure 4, figure 5 shows the temperature at the distal end of the aerosol-forming substrate measured at a position 11 millimetres from the distal end of the combustible heat source, which corresponds to position T in figure 1₃. The temperature profile was again measured using an electron temperature probe inserted approximately 2mm deep into the aerosol-forming substrate of the aerosol-generating article.

In figure 5, the line labeled "SMAR" 30 shows the temperature profile of an aerosol-generating article having a "bare" combustible heat source. In other words, the "SMAR" line 22 shows the temperature profile of an aerosol-generating article without a layer of material substantially surrounding the length of the combustible heat source.

In figure 5, the "cellophane" line labelled 31 shows the temperature profile of an aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source. The length of ceramic paper substantially surrounding the combustible heat source in the "glassine" test is ceramic paper comprising glass fibres. The ceramic paper comprising glass fibres, which extends from the distal end of the combustible heat source and from the distal end of the aerosol-forming substrate over the entire length of the combustible heat source, has a thickness of about 1 mm and a length of about 5.5 mm.

In figure 5, the line of "biosoluble fibres" labelled 32 shows the temperature profile of an aerosol-generating article having a layer of ceramic paper substantially surrounding the length of the combustible heat source. The length of ceramic paper substantially surrounding the combustible heat source in the "ceramic paper 1" test was purchased from Morgan Advanced Materials, plcPlus Fibre。The Plus fiber comprises biosoluble alkaline earth silicate fiber. The ceramic paper comprising biosoluble fibres may have a thickness of about 0.5 millimetres and a length of about 5.5 millimetres, the ceramic paper extending from the distal end of the combustible heat source and from the distal end of the aerosol-forming substrate over the entire length of the combustible heat source.

Surprisingly, as shown in figure 5, it has been found that the temperature profile 32 of an aerosol-generating article having a ceramic paper layer comprising biosoluble alkaline earth silicate fibres shows a higher temperature after a period of time of about 200 seconds than both the temperature profile 30 of an aerosol-generating article without a material layer substantially surrounding the length of the combustible heat source and the temperature profile 31 of an aerosol-generating article having a ceramic paper layer comprising glass fibres after a period of time of 200 seconds.

This surprising result shows that smoke generation time can be increased by providing the aerosol-forming article with a ceramic paper layer comprising biosoluble alkaline earth silicate fibres of a length substantially surrounding the combustible heat source, even when compared to an article having a ceramic paper layer comprising glass fibres of a length substantially surrounding the combustible heat source.

After ignition of the heat source, the aerosol-generating articles according to the invention were tested by observing their effect by placing them on Whatmann paper. For example, aerosol-forming articles are conditioned at about 23 ℃ ± 3 ℃ and 55% ± 5% relative humidity for 24 hours. The adjusted aerosol-generating article was ignited using an electric lighter and allowed to burn for a period of 2 minutes. After 2 minutes, the aerosol-generating article is placed on a stack of Whatmann paper for a period of 10 minutes. After 10 minutes, the Whatmann paper was inspected. It was observed that aerosol-generating articles having the layer of ceramic paper substantially surrounding the combustible heat source did not produce holes in any of the Whatmann papers and did not produce small brown regions in the top paper. This result shows that the layer of ceramic paper having a length substantially surrounding the combustible heat source reduces the surface temperature close to the heat source.

A schematic view of a second embodiment of an aerosol-generating article according to the present invention is shown in figure 6. The aerosol-generating article 102 is substantially similar to the aerosol-generating article 2 shown in figure 1. The aerosol-generating article 102 comprises a combustible heat source 103, an aerosol-forming substrate 104, a layer of ceramic paper 105 and a layer of cigarette paper 107, which are arranged similarly to the corresponding components of the aerosol-generating article 2 shown in figure 1. However, the combustible heat source 103 is a non-blind type heat source. The non-clogging heat source 103 includes an annular body 115 of carbonaceous material having a passageway 116 extending between a distal end face and a proximal end face. The passageways 116 form part of an airflow path through the aerosol-generating article and enable air to be drawn from the proximal end of the aerosol-generating article through the combustible heat source 103 and to the aerosol-forming substrate 104. The layer of ceramic paper 105 is spaced from the airflow path through the aerosol-generating article 102 such that air drawn through the airflow path does not contact the layer of ceramic paper 105.

A non-combustible, substantially air impermeable first barrier 106 is arranged between the proximal end of the combustible heat source 103 and the distal end of the aerosol-forming substrate 104, similar to the first barrier 6 described above with respect to figure 1. However, unlike the first barrier 6 described above, the first barrier 106 includes apertures 120 aligned with the passages 116 to enable air to pass from the passages 116 to the aerosol-forming substrate 104.

A non-combustible, substantially gas impermeable second barrier 117 is coated on the inner surface of the passageway 116. The second barrier 117 isolates air passing through the passageway 116 from the combustible heat sources 103 and the combustion products of the combustible heat sources.

As the combustible heat source 103 is a non-blind heat source, the aerosol-generating article 102 does not comprise an air inlet arranged at the aerosol-forming substrate 104. When a user draws on the mouthpiece of the aerosol-generating article 102, ambient air may be drawn through the heat source 103 into the aerosol-generating article 102 through the passageway 116. Air drawn into the aerosol-generating article 102 may flow along the airflow path of the aerosol-generating article 102 through the passages 116, through the aerosol-forming substrate 104, the transfer element, the cooling element and the spacing element to the mouthpiece, and out of the mouthpiece for inhalation by a user. The general direction of airflow through the aerosol-generating article 102 is indicated by the arrows.

It will be appreciated that in some embodiments, other air inlets may be provided in the aerosol-generating article in addition to the air passage through the combustible heat source.

The specific embodiments described above are intended to be illustrative of the invention. However, other embodiments may be made without departing from the scope of the invention as defined in the claims, and it is to be understood that the specific embodiments described above are not intended to be limiting.

Claims

1. An aerosol-generating article comprising:

an aerosol-forming substrate;

a combustible heat source;

at least one layer of ceramic paper surrounding at least part of the length of the combustible heat source,

wherein the at least one layer of ceramic paper comprises a cellulose derivative binder, and wherein the ceramic paper comprises at least one of:

a biosoluble fiber;

low biopersistent fiber; and

a fiber comprising at least one of silica, calcium oxide, and magnesium oxide.

2. An aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper comprises less than or equal to about 40 weight percent of cellulose derivative binder.

3. An aerosol-generating article according to claim 1 or claim 2, wherein the ceramic paper comprises fibres comprising an alkaline earth silicate.

4. An aerosol-generating article according to any preceding claim, comprising one or more airflow paths along which air may be drawn through the aerosol-generating article for inhalation by a user.

5. An aerosol-generating article according to any preceding claim comprising one or more non-combustible, substantially air-impermeable barriers between the combustible heat source and the aerosol-forming substrate.

6. An aerosol-generating article according to claim 5, wherein the non-combustible, substantially air-impermeable barrier between the combustible heat source and the aerosol-forming substrate comprises a first barrier contiguous with one or both of a proximal end of the combustible heat source and a distal end of the aerosol-forming substrate.

7. An aerosol-generating article according to any preceding claim, wherein the at least one layer of ceramic paper is isolated from the one or more airflow paths such that, in use, air drawn through the aerosol-generating article along the one or more airflow paths does not directly contact the at least one layer of ceramic paper.

8. An aerosol-generating article according to any preceding claim, wherein the combustible heat source, the aerosol-forming substrate and the at least one layer of ceramic paper are arranged such that the temperature of the aerosol-forming substrate does not exceed 375 ℃ during combustion of the combustible heat source.

9. An aerosol-generating article according to any preceding claim, wherein the ceramic paper comprises at least about 50 weight percent ceramic material.

10. An aerosol-generating article according to any preceding claim, wherein the at least one layer of ceramic paper has a thickness of between about 0.5 mm and about 5 mm.

11. A method of forming an aerosol-generating article according to claims 1 to 10, the method comprising:

arranging a combustible heat source to heat the aerosol-forming substrate;

and

surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper comprising a cellulose derivative binder.

12. A method of forming an aerosol-generating article according to claim 11, wherein surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper comprises:

providing a banded ceramic paper having opposite ends comprising a cellulose derivative binder;

wrapping the strip around the combustible heat source such that the combustible heat source is surrounded by at least one layer of ceramic paper;

overlapping the opposite ends of the strip; and

securing the overlapping ends together to secure the at least one layer of ceramic paper to the combustible heat source.

13. A method of forming an aerosol-generating article according to claim 11, wherein surrounding at least a portion of the length of the combustible heat source with at least one layer of ceramic paper comprises:

applying an adhesive layer to one side of the strip at least at each of the opposite ends;

arranging the strip with the adhesive layer facing the combustible heat source;

wrapping the strip around the combustible heat source such that the combustible heat source is surrounded by the at least one layer of ceramic paper;

abutting said opposite ends of said strip without overlapping said opposite ends; and

securing the strip to the combustible heat source using the adhesive layer.