Method for making a combustible heat source comprising carbon and a binder

Abstract

A method for making a combustible heat source for an aerosol-generating article, the method comprising: forming a combustible heat source comprising carbon and a binder, the binder comprising polyvinyl alcohol; and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes.

Description

[Technical Field]

[0001] The present invention relates to a method for creating a combustible heat source for an aerosol-generating article, and to an aerosol-generating article including the combustible heat source created by the method and an aerosol-forming substrate located downstream of the combustible heat source. [Background technology]

[0002] Many aerosol-generating articles in which tobacco material is heated rather than burned have been proposed in the art. One purpose of such heated aerosol-generating articles is to reduce known harmful smoke components of the type produced by the combustion and pyrolytic decomposition of tobacco in conventional cigarettes.

[0003] In heated aerosol-generating articles, the aerosol is typically generated by heat transfer from a heat source, e.g., a chemical, electrical, or combustible heat source, to a physically separate aerosol-forming substrate that may be located within, around, or downstream from the heat source.

[0004] In one type of heated aerosol-generating article, an aerosol is generated by heat transfer from a combustible carbonaceous heat source to a physically separate aerosol-forming substrate containing tobacco material located downstream of the combustible carbonaceous heat source. During use, volatile compounds are released from the tobacco material by heat transfer from the combustible carbonaceous heat source to the aerosol-forming substrate and are entrained in air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol that is inhaled by the user.

[0005] Heat can be transferred from the combustible carbonaceous heat source to the aerosol-forming substrate by one or both of forced convection and conduction.

[0006] To ensure sufficient conductive heat transfer from the combustible carbonaceous heat source to the aerosol-forming substrate to obtain an acceptable aerosol, it is known to include a heat-conducting element around and in direct contact with at least a rear portion of the combustible carbonaceous heat source and at least a front portion of the aerosol-forming substrate of the aerosol-generating article. For example, WO2009 / 022232A2 discloses a smoking article comprising a combustible carbonaceous heat source, an aerosol-forming substrate downstream of the combustible heat source, and a heat-conducting element around and in direct contact with the rear portion of the combustible carbonaceous heat source and the adjacent front portion of the aerosol-forming substrate. During use, the heat generated during the combustion of the combustible carbonaceous heat source is transferred to the periphery of the front portion of the aerosol-forming substrate by conduction through the adjacent downstream end of the combustible carbonaceous heat source and the heat-conducting element.

[0007] The combustion temperature of a combustible heat source for a heated aerosol-generating article should not be so high as to result in combustion or thermal decomposition of the aerosol-forming substrate during use of the heated aerosol-generating article, but should be high enough to generate enough heat to release enough volatile compounds from the aerosol-forming substrate to produce an acceptable aerosol, especially early in the puff.

[0008] A variety of combustible carbonaceous heat sources for heated aerosol-generating articles are known in the art.

[0009] When used in heated aerosol-generating articles, known combustible carbonaceous heat sources often do not produce sufficient heat after their ignition to produce an acceptable aerosol during the initial puff.

[0010] When used in heated aerosol-generating articles, known combustible carbonaceous heat sources are often difficult to ignite. Failure to properly ignite a combustible carbonaceous heat source in a heated aerosol-generating article can lead to the delivery of an unacceptable aerosol to a user.

[0011] The inclusion of oxidizers and other additives in combustible carbonaceous heat sources has been proposed in the art to improve their ignition and combustion characteristics. For example, WO2012 / 164077A1 discloses a combustible heat source for a smoking article comprising carbon and at least one ignition aid selected from the group consisting of metal nitrates, chlorates, peroxides, thermic materials, intermetallic materials, magnesium, zirconium, and combinations thereof, having a thermal decomposition temperature of less than about 600 degrees Celsius.

[0012] Some ignition aids used in known combustible carbonaceous heat sources have been found to decompose when exposed to environmental conditions during transportation and storage of the combustible carbonaceous heat source. For example, some ignition aids used in known combustible carbonaceous heat sources have been found to decompose when exposed to atmospheric moisture during transportation and storage of the combustible carbonaceous heat source. Decomposition of the ignition aid during transportation and storage can disadvantageously make it more difficult to ignite known carbonaceous combustible heat sources that include the ignition aid.

[0013] It would be desirable to provide a combustible carbonaceous heat source that exhibits improved shelf life compared to known combustible carbonaceous heat sources.

[0014] In particular, it would be desirable to provide a combustible carbonaceous heat source that includes an ignition aid that exhibits rapid ignition and mechanical integrity, even after exposure to environmental conditions. Summary of the Invention

[0015] The present invention relates to a method for making a combustible heat source for an aerosol-generating article. The method may include forming the combustible heat source. The combustible heat source may include carbon. The combustible heat source may include a binder. The binder may include polyvinyl alcohol. The method may include heating the formed combustible heat source. The method may include heating the formed combustible heat source to a temperature of at least about 90 degrees Celsius. The method may include heating the formed combustible heat source for at least about 45 minutes.

[0016] According to the present invention, there is provided a method for making a combustible heat source for an aerosol-generating article, the method comprising: forming a combustible heat source comprising carbon and a binder, the binder comprising polyvinyl alcohol; and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes.

[0017] The present invention also provides a combustible heat source made by a method according to the present invention.

[0018] The present invention further provides an aerosol-generating article comprising a combustible heat source made by a method according to the present invention and an aerosol-forming substrate downstream of the combustible heat source.

[0019] Surprisingly, it has been discovered that forming a combustible heat source comprising carbon and a binder, where the binder comprises polyvinyl alcohol, and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes can advantageously improve the shelf life of the combustible heat source.

[0020] In particular, it has surprisingly been discovered that forming a combustible heat source comprising carbon and a binder, where the binder comprises polyvinyl alcohol, and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes can advantageously reduce decomposition of one or more moisture-sensitive components of the combustible heat source as a result of exposure to environmental conditions.

[0021] Heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes can advantageously reduce decomposition of moisture-sensitive components of the combustible heat source as a result of exposure to high humidity.

[0022] For example, it has surprisingly been discovered that forming a combustible heat source comprising carbon, a binder, and an ignition aid, wherein the binder comprises polyvinyl alcohol and an ignition aid comprising an alkaline earth metal peroxide, and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes can advantageously reduce decomposition of the ignition aid as a result of exposure to high humidity.

[0023] Forming a combustible heat source comprising carbon and a binder, wherein the binder comprises polyvinyl alcohol, and heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes may advantageously improve the chemical and physical stability of the combustible heat source made by a method according to the present invention during transportation and storage of the combustible heat source by reducing decomposition of one or more moisture-sensitive components of the combustible heat source.

[0024] Without intending to be bound by theory, forming a combustible heat source comprising carbon and a binder, the binder comprising polyvinyl alcohol, creates a barrier to moisture diffusion into the combustible heat source.

[0025] Without intending to be bound by theory, it is believed that heating the formed flammable heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes changes the structure of the polyvinyl alcohol from a more amorphous state to a more crystalline state, which is believed to enhance the effectiveness of the polyvinyl alcohol as a barrier to moisture diffusion into the flammable heat source.

[0026] Without intending to be bound by theory, it is believed that heating the formed combustible heat source at a temperature of at least about 90 degrees Celsius for at least about 45 minutes may result in a chemical reaction between the polyvinyl alcohol and other components of the combustible heat source, which may also improve the shelf life of the combustible heat source.

[0027] The combustible heat source produced by the method according to the present invention is a solid combustible heat source.

[0028] The combustible heat source produced by the method according to the present invention is preferably a solid, monolithic combustible heat source, i.e. a one-piece, solid, combustible heat source.

[0029] The combustible heat source produced by the method according to the present invention is a carbonaceous heat source.

[0030] As used herein in connection with the present invention, the term "carbonaceous" is used to describe a combustible heat source that contains carbon.

[0031] The combustible heat source produced by the method according to the present invention comprises carbon as a fuel.

[0032] The method can include forming a combustible heat source that includes at least about 25 weight percent carbon.

[0033] Unless otherwise specified, the weight percentages of the components of the combustible heat source listed herein are based on the total dry weight of the formed combustible heat source.

[0034] Preferably, the method includes forming a combustible heat source that includes at least about 30 weight percent carbon.

[0035] More preferably, the method includes forming a combustible heat source that includes at least about 35 weight percent carbon.

[0036] The method can include forming a combustible heat source that includes about 40 weight percent or less carbon.

[0037] The method can include forming a combustible heat source that includes about 60 weight percent or less carbon.

[0038] Preferably, the method includes forming a combustible heat source that includes no more than about 55 weight percent carbon.

[0039] More preferably, the method includes forming a combustible heat source that includes about 50 weight percent or less carbon.

[0040] The method can include forming a combustible heat source that includes about 45 weight percent or less carbon.

[0041] The method can include forming a combustible heat source that includes about 25 weight percent to about 60 weight percent carbon, about 25 weight percent to about 55 weight percent carbon, about 25 weight percent to about 50 weight percent carbon, or about 25 weight percent to about 45 weight percent carbon.

[0042] Preferably, the method includes forming a combustible heat source that includes about 30 weight percent to about 60 weight percent carbon, about 30 weight percent to about 55 weight percent carbon, about 30 weight percent to about 50 weight percent carbon, or about 30 weight percent to about 45 weight percent carbon.

[0043] More preferably, the method includes forming a combustible heat source that includes about 35 weight percent to about 60 weight percent carbon, about 35 weight percent to about 55 weight percent carbon, about 35 weight percent to about 50 weight percent carbon, or about 35 weight percent to about 45 weight percent carbon.

[0044] The method may include forming a combustible heat source comprising about 40 weight percent to about 60 weight percent carbon, about 40 weight percent to about 55 weight percent carbon, about 40 weight percent to about 50 weight percent carbon, or about 40 weight percent to about 45 weight percent carbon.

[0045] The method may include forming the combustible heat source using one or more suitable carbon materials, which are known in the art and include, but are not limited to, carbon powder and charcoal powder.

[0046] Advantageously, the method may include forming a combustible heat source comprising one or more carbonizable materials.

[0047] The method includes forming a combustible heat source including carbon and a binder.

[0048] As used herein in connection with the present invention, the term "binder" is used to describe a component of the combustible heat source that is capable of binding together carbon and any other components of the combustible heat source.

[0049] The method can include forming a combustible heat source that includes at least about 3 weight percent binder.

[0050] Preferably, the method includes forming a combustible heat source that includes at least about 4 weight percent binder.

[0051] More preferably, the method includes forming a combustible heat source that includes at least about 5 weight percent binder.

[0052] The method can include forming a combustible heat source that includes up to about 20 weight percent of a binder.

[0053] Preferably, the method includes forming a combustible heat source that includes about 15 weight percent or less of a binder.

[0054] More preferably, the method includes forming a combustible heat source that includes about 10 weight percent or less of a binder.

[0055] The method can include forming a combustible heat source including about 3 weight percent to about 20 weight percent binder, about 3 weight percent to about 15 weight percent binder, or about 3 weight percent to about 10 weight percent binder.

[0056] Preferably, the method includes forming a combustible heat source including about 4 weight percent to about 20 weight percent binder, about 4 weight percent to about 15 weight percent binder, or about 4 weight percent to about 10 weight percent binder.

[0057] More preferably, the method includes forming a combustible heat source including about 5 weight percent to about 20 weight percent binder, about 5 weight percent to about 15 weight percent binder, or about 5 weight percent to about 10 weight percent binder.

[0058] The method includes forming a combustible heat source including carbon and a binder, the binder including polyvinyl alcohol.

[0059] The method can include forming a combustible heat source that includes at least about 0.1 weight percent polyvinyl alcohol.

[0060] Preferably, the method includes forming a combustible heat source that includes at least about 0.25 weight percent polyvinyl alcohol.

[0061] More preferably, the method includes forming a combustible heat source that includes at least about 0.5 weight percent polyvinyl alcohol.

[0062] The method can include forming a combustible heat source that includes at least about 0.75 weight percent polyvinyl alcohol.

[0063] The method can include forming a combustible heat source that includes up to about 5 weight percent polyvinyl alcohol.

[0064] The method can include forming a combustible heat source that includes up to about 4 weight percent polyvinyl alcohol.

[0065] Preferably, the method includes forming a combustible heat source that includes about 3 weight percent or less polyvinyl alcohol.

[0066] More preferably, the method includes forming a combustible heat source that includes about 2 weight percent or less polyvinyl alcohol.

[0067] The method can include forming a combustible heat source including about 0.1 weight percent to about 5 weight percent polyvinyl alcohol, about 0.1 weight percent to about 4 weight percent polyvinyl alcohol, or about 0.1 weight percent to about 3 weight percent polyvinyl alcohol, or about 0.1 weight percent to about 2 weight percent polyvinyl alcohol.

[0068] Preferably, the method may include forming a combustible heat source comprising about 0.25 weight percent to about 5 weight percent polyvinyl alcohol, about 0.25 weight percent to about 4 weight percent polyvinyl alcohol, or about 0.25 weight percent to about 3 weight percent polyvinyl alcohol, or about 0.25 weight percent to about 2 weight percent polyvinyl alcohol.

[0069] More preferably, the method may include forming a combustible heat source comprising about 0.5 weight percent to about 5 weight percent polyvinyl alcohol, about 0.5 weight percent to about 4 weight percent polyvinyl alcohol, or about 0.5 weight percent to about 3 weight percent polyvinyl alcohol, or about 0.5 weight percent to about 2 weight percent polyvinyl alcohol.

[0070] The method may include forming a combustible heat source including about 0.75 weight percent to about 5 weight percent polyvinyl alcohol, about 0.75 weight percent to about 4 weight percent polyvinyl alcohol, or about 0.75 weight percent to about 3 weight percent polyvinyl alcohol, or about 0.75 weight percent to about 2 weight percent polyvinyl alcohol.

[0071] The method can include forming a combustible heat source including polyvinyl alcohol having a molecular weight of at least about 10,000 grams / mole.

[0072] Preferably, the method includes forming a combustible heat source comprising polyvinyl alcohol having a molecular weight of at least about 20,000 grams / mole.

[0073] The method can include forming a combustible heat source that includes polyvinyl alcohol having a molecular weight of about 200,000 grams / mole or less.

[0074] Preferably, the method includes forming a combustible heat source comprising polyvinyl alcohol having a molecular weight of about 125,000 grams / mole or less.

[0075] The method can include forming a combustible heat source including polyvinyl alcohol having a molecular weight of about 10,000 grams / mole to about 200,000 grams / mole, or about 10,000 grams / mole to about 125,000 grams / mole.

[0076] Preferably, the method includes forming a combustible heat source including forming a combustible heat source comprising polyvinyl alcohol having a molecular weight of about 20,000 grams / mole to about 200,000 grams / mole, or about 20,000 grams / mole to about 125,000 grams / mole.

[0077] Preferably, the method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of one or more cellulose ethers and polyvinyl alcohol.

[0078] More preferably, the method includes forming a combustible heat source comprising carbon and a binder, wherein the binder comprises one or more cellulose ethers selected from the group consisting of carboxymethyl cellulose, ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose in combination with polyvinyl alcohol.

[0079] Most preferably, the method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose and polyvinyl alcohol.

[0080] The method can include forming a combustible heat source that includes at least about 1.5 weight percent carboxymethyl cellulose.

[0081] Preferably, the method includes forming a combustible heat source that includes at least about 2 weight percent carboxymethyl cellulose.

[0082] More preferably, the method includes forming a combustible heat source that includes at least about 3 weight percent carboxymethyl cellulose.

[0083] The method can include forming a combustible heat source that includes up to about 15 weight percent carboxymethyl cellulose.

[0084] Preferably, the method includes forming a combustible heat source that includes about 12 weight percent or less carboxymethyl cellulose.

[0085] More preferably, the method includes forming a combustible heat source that includes about 8 percent by weight or less carboxymethyl cellulose.

[0086] The method can include forming a combustible heat source including about 1.5 weight percent to about 15 weight percent carboxymethyl cellulose, about 1.5 weight percent to about 12 weight percent carboxymethyl cellulose, or about 1.5 weight percent to about 8 weight percent carboxymethyl cellulose.

[0087] Preferably, the method includes forming a combustible heat source comprising about 2 weight percent to about 15 weight percent carboxymethyl cellulose, about 2 weight percent to about 12 weight percent carboxymethyl cellulose, or about 2 weight percent to about 8 weight percent carboxymethyl cellulose.

[0088] More preferably, the method includes forming a combustible heat source comprising about 3 weight percent to about 15 weight percent carboxymethyl cellulose, about 3 weight percent to about 12 weight percent carboxymethyl cellulose, or about 3 weight percent to about 8 weight percent carboxymethyl cellulose.

[0089] The method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is at least about 1:1.

[0090] Preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is at least about 3:2.

[0091] More preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is at least about 2:1.

[0092] The method may include forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is about 4:1 or less.

[0093] Preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is about 7:2 or less.

[0094] More preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is about 3:1 or less.

[0095] The method may include forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is about 5:2 or less.

[0096] The method may include forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of the weight percent of carboxymethyl cellulose to the weight percent of polyvinyl alcohol in the combustible heat source is between about 1:1 and about 4:1, between about 1:1 and about 7:2, between about 1:1 and about 3:1, or between about 1:1 and about 5:2.

[0097] Preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is between about 3:2 and about 4:1, between about 3:2 and about 7:2, between about 3:2 and about 3:1, or between about 3:2 and about 5:2.

[0098] More preferably, the method includes forming a combustible heat source comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, wherein the ratio of weight percent of carboxymethyl cellulose to weight percent of polyvinyl alcohol in the combustible heat source is between about 2:1 and about 4:1, between about 2:1 and about 7:2, between about 2:1 and about 3:1, or between about 2:1 and about 5:2.

[0099] The method includes forming a combustible heat source including carbon and a binder, the binder including a combination of carboxymethyl cellulose, one or more additional cellulose ethers, and polyvinyl alcohol.

[0100] As used herein in connection with the present invention, the term "additional cellulose ethers" is used to describe cellulose ethers other than carboxymethyl cellulose.

[0101] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, one or more additional cellulose ethers selected from the group consisting of ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, and polyvinyl alcohol.

[0102] The method includes forming a combustible heat source including carbon and a binder, the binder including a combination of polyvinyl alcohol and one or more additional non-cellulosic film-forming polymers.

[0103] As used herein in connection with the present invention, the term "non-cellulosic film-forming polymer" is used to describe a non-cellulosic polymer that is capable of forming a film upon application to a solid surface.

[0104] As used herein in connection with the present invention, the term "additional non-cellulosic film-forming polymer" is used to describe non-cellulosic film-forming polymers other than polyvinyl alcohol.

[0105] The method includes forming a combustible heat source including carbon and a binder, the binder including a combination of one or more cellulose ethers, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers.

[0106] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of one or more cellulose ethers selected from the group consisting of carboxymethyl cellulose, ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers.

[0107] The method may include forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers.

[0108] The method may include forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, one or more additional cellulose ethers, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers.

[0109] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, one or more additional cellulose ethers selected from the group consisting of ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers.

[0110] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of polyvinyl alcohol and one or more additional non-cellulosic film-forming polymers selected from the group consisting of polyvinyl acetate, polyethylene glycol, polyvinylpyrrolidone, and graft copolymers thereof.

[0111] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of one or more cellulose ethers selected from the group consisting of carboxymethyl cellulose, ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers selected from the group consisting of polyvinyl acetate, polyethylene glycol, polyvinylpyrrolidone, and graft copolymers thereof.

[0112] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, polyvinyl alcohol, and a combination of one or more additional non-cellulosic film-forming polymers selected from the group consisting of polyvinyl acetate, polyethylene glycol, polyvinylpyrrolidone, and graft copolymers thereof.

[0113] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, one or more additional cellulose ethers, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers selected from the group consisting of polyvinyl acetate, polyethylene glycol, polyvinylpyrrolidone, and graft copolymers thereof.

[0114] The method includes forming a combustible heat source comprising carbon and a binder, the binder comprising a combination of carboxymethyl cellulose, one or more additional cellulose ethers selected from the group consisting of ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose, polyvinyl alcohol, and one or more additional non-cellulosic film-forming polymers selected from the group consisting of polyvinyl acetate, polyethylene glycol, polyvinylpyrrolidone and graft copolymers thereof.

[0115] Preferably, the method includes forming a combustible heat source including carbon, a binder, and an ignition aid.

[0116] As used herein with respect to the present invention, the term "ignition aid" is used to mean a material that releases energy and / or oxygen during ignition of a combustible heat source when the rate of release of energy and / or oxygen by the material is not ambient oxygen diffusion limited. In other words, the rate of release of energy and / or oxygen by the material during ignition of a combustible heat source is largely independent of the rate at which ambient oxygen can reach the material. Also, as used herein, the term "ignition aid" is used to mean an elemental metal that releases energy during ignition of a combustible carbonaceous heat source, wherein the ignition temperature of the elemental metal is less than about 500 degrees Celsius and the heat of combustion of the elemental metal is at least about 5 kilojoules / gram.

[0117] As used herein in connection with the present invention, the term "ignition aid" does not include alkali metal salts of carboxylic acids (such as alkali metal citrates, acetates, and succinates), alkali metal halide salts (such as alkali metal chlorides), alkali metal carbonates, or alkali metal phosphates, which are believed to modify carbon combustion. Such alkali metal combustion salts, even when present in large amounts relative to the total weight of the combustible heat source, do not release enough energy during ignition of the combustible heat source to produce an acceptable aerosol during the initial puff.

[0118] Examples of suitable ignition aids include, but are not limited to, energetic materials that react exothermically with oxygen upon ignition of the combustible carbonaceous heat source; thermic materials comprising a reducing agent, e.g., a metal, and an oxidizing agent, e.g., a metal oxide, that react with each other to release energy upon ignition of the combustible carbonaceous heat source; materials that react exothermically upon ignition of the combustible carbonaceous heat source, e.g., intermetallic and bimetallic materials, metal carbides and metal hydrides; and oxidizing agents that decompose to release oxygen upon ignition of the combustible carbonaceous heat source.

[0119] Examples of suitable energetic materials include, but are not limited to, aluminum, iron, magnesium, and zirconium.

[0120] Examples of suitable oxidizing agents include, but are not limited to, nitrates, nitrites, chlorates, chlorites, bromates, perbromates, bromites, borates, ferrates, sulfates, ferrites, manganates, permanganates, peroxides, superoxides, iodates, periodates, iodites, sulfates, sulfites, sulfoxides, phosphates, phospinates, phosphites, and phosphanites.

[0121] Preferably, the method includes forming a combustible heat source including carbon, a binder, and an ignition aid, wherein the ignition aid is selected from the group consisting of metal nitrates, chlorates, peroxides, thermite materials, intermetallic materials, magnesium, zirconium, and combinations thereof, having a thermal decomposition temperature of less than 600 degrees Celsius.

[0122] The amount of energy and / or oxygen released by the ignition aid during ignition of the combustible heat source may be sufficient to cause the combustible heat source to undergo a two-stage combustion process.

[0123] In an initial first stage, a combustible heat source including an ignition aid made by a method according to the present invention may exhibit a "boost" in temperature, and then in a second stage, a combustible heat source including an ignition aid made by a method according to the present invention may undergo sustained combustion at a lower "cruise" temperature.

[0124] An initial "boost" in the temperature of a combustible heat source containing an ignition aid made by a method according to the present invention may occur due to very rapid heat propagation throughout the combustible heat source upon ignition of a portion thereof. The very rapid heat propagation may be the result of a chain reaction in which a portion of the combustible heat source that ignites causes adjacent unlit portions of the combustible heat source to ignite.

[0125] In use in an aerosol-generating article according to the present invention, a rapid increase in the temperature of a combustible heat source comprising an ignition aid made by a method according to the present invention to a "boost" temperature can rapidly raise the temperature of the aerosol-forming substrate to a level at which volatile compounds are released from the aerosol-forming substrate. This can ensure that the aerosol-generating article according to the present invention produces a sensory-acceptable aerosol during the initial puff. A subsequent decrease in the temperature of the combustible heat source to a "cruise" temperature can ensure that the temperature of the aerosol-forming substrate does not reach a level at which combustion or thermal decomposition of the aerosol-forming substrate occurs.

[0126] Controlling the temperature of the combustible heat source produced by the method according to the invention in the manner described above may advantageously enable an aerosol-generating article according to the invention not only to produce a sensory acceptable aerosol during the initial puff, but also to substantially avoid combustion or thermal decomposition of the aerosol-forming substrate.

[0127] The amount of ignition aid that must be included to achieve the two-step process described above will vary depending on the particular ignition aid included in the combustible heat source produced by the method of the present invention.

[0128] Generally, the more energy and / or oxygen released by the ignition aid per unit mass thereof, the less ignition aid must be included in the combustible heat source produced by the method of the present invention to achieve the two-stage combustion process described above.

[0129] More preferably, the method includes forming a combustible heat source comprising carbon, a binder, and an ignition aid, the ignition aid comprising an alkaline earth metal peroxide.

[0130] As used herein in connection with the present invention, the term "alkaline earth metal peroxide ignition aid" is used to describe an alkaline earth metal peroxide that releases energy and / or oxygen during ignition of a combustible heat source, wherein the rate of release of energy and / or oxygen by the alkaline earth metal peroxide is not ambient oxygen diffusion limited. In other words, the rate of release of energy and / or oxygen by the alkaline earth metal peroxide during ignition of a combustible heat source is largely independent of the rate at which ambient oxygen can reach the alkaline earth metal peroxide.

[0131] The method can include forming a combustible heat source that includes at least about 15 weight percent of an alkaline earth metal peroxide ignition aid.

[0132] Preferably, the method includes forming a combustible heat source that includes at least about 20 weight percent alkaline earth metal peroxide ignition aid.

[0133] More preferably, the method includes forming a combustible heat source that includes at least about 30 weight percent alkaline earth metal peroxide ignition aid.

[0134] The method can include forming a combustible heat source that includes at least about 40 weight percent of an alkaline earth metal peroxide ignition aid.

[0135] The method can include forming a combustible heat source that includes up to about 65 weight percent of an alkaline earth metal peroxide ignition aid.

[0136] Preferably, the method includes forming a combustible heat source that includes up to about 60 weight percent of an alkaline earth metal peroxide ignition aid.

[0137] More preferably, the method includes forming a combustible heat source that includes up to about 55 weight percent alkaline earth metal peroxide ignition aid.

[0138] The method can include forming a combustible heat source that includes up to about 50 weight percent of an alkaline earth metal peroxide ignition aid.

[0139] The method can include forming a combustible heat source including about 15 weight percent to about 65 weight percent alkaline earth metal peroxide ignition aid, about 15 weight percent to about 60 weight percent alkaline earth metal peroxide ignition aid, about 15 weight percent to about 55 weight percent alkaline earth metal peroxide ignition aid, or about 15 weight percent to about 50 weight percent alkaline earth metal peroxide ignition aid.

[0140] Preferably, the method includes forming a combustible heat source including about 20 weight percent to about 65 weight percent alkaline earth metal peroxide ignition aid, about 20 weight percent to about 60 weight percent alkaline earth metal peroxide ignition aid, about 20 weight percent to about 55 weight percent alkaline earth metal peroxide ignition aid, or about 20 weight percent to about 50 weight percent alkaline earth metal peroxide ignition aid.

[0141] More preferably, the method includes forming a combustible heat source comprising about 30 weight percent to about 65 weight percent alkaline earth metal peroxide ignition aid, about 30 weight percent to about 60 weight percent alkaline earth metal peroxide ignition aid, about 30 weight percent to about 55 weight percent alkaline earth metal peroxide ignition aid, or about 30 weight percent to about 50 weight percent alkaline earth metal peroxide ignition aid.

[0142] The method can include forming a combustible heat source including about 40 weight percent to about 65 weight percent alkaline earth metal peroxide ignition aid, about 40 weight percent to about 60 weight percent alkaline earth metal peroxide ignition aid, about 40 weight percent to about 55 weight percent alkaline earth metal peroxide ignition aid, or about 40 weight percent to about 50 weight percent alkaline earth metal peroxide ignition aid.

[0143] Most preferably, the method includes forming a combustible heat source comprising carbon, a binder, and an ignition aid, the ignition aid comprising calcium peroxide.

[0144] The method can include forming a combustible heat source that includes at least about 15 weight percent calcium peroxide.

[0145] Preferably, the method includes forming a combustible heat source that includes at least about 20 weight percent calcium peroxide.

[0146] More preferably, the method includes forming a combustible heat source that includes at least about 30 weight percent calcium peroxide.

[0147] The method can include forming a combustible heat source that includes at least about 40 weight percent calcium peroxide.

[0148] The method can include forming a combustible heat source including up to about 65 weight percent calcium peroxide.

[0149] Preferably, the method includes forming a combustible heat source that includes up to about 60 weight percent calcium peroxide.

[0150] More preferably, the method includes forming a combustible heat source that includes about 55 weight percent or less calcium peroxide.

[0151] The method can include forming a combustible heat source that includes up to about 50 weight percent calcium peroxide.

[0152] The method can include forming a combustible heat source including about 15 weight percent to about 65 weight percent calcium peroxide, about 15 weight percent to about 60 weight percent calcium peroxide, about 15 weight percent to about 55 weight percent calcium peroxide, or about 15 weight percent to about 50 weight percent calcium peroxide.

[0153] Preferably, the method includes forming a combustible heat source comprising about 20 weight percent to about 65 weight percent calcium peroxide, about 20 weight percent to about 60 weight percent calcium peroxide, about 20 weight percent to about 55 weight percent calcium peroxide, or about 20 weight percent to about 50 weight percent calcium peroxide.

[0154] More preferably, the method includes forming a combustible heat source comprising about 30 weight percent to about 65 weight percent calcium peroxide, about 30 weight percent to about 60 weight percent calcium peroxide, about 30 weight percent to about 55 weight percent calcium peroxide, or about 30 weight percent to about 50 weight percent calcium peroxide.

[0155] The method can include forming a combustible heat source including about 40 weight percent to about 65 weight percent calcium peroxide, about 40 weight percent to about 60 weight percent calcium peroxide, about 40 weight percent to about 55 weight percent calcium peroxide, or about 40 weight percent to about 50 weight percent calcium peroxide.

[0156] The method can include forming a combustible heat source including carbon, a binder, and one or more carboxylate combustion salts.

[0157] The method can include forming a combustible heat source including carbon, a binder, an ignition aid, and one or more carboxylate combustion salts.

[0158] As used herein in connection with the present invention, the term "carboxylate combustion salt" is used to describe salts of carboxylic acids other than carbonic acid, i.e., as used herein in connection with the present invention, the term "carboxylate combustion salt" does not include carbonates or bicarbonates.

[0159] One or more carboxylate combustion salts may advantageously promote the combustion of a combustible heat source.

[0160] The carboxylate combustion salts may include monovalent, divalent, or trivalent cations and carboxylate anions.

[0161] The carboxylate combustion salts may include monovalent, divalent, or trivalent cations and acetate, citrate, or succinate anions.

[0162] The carboxylate combustion salt may be an alkali metal carboxylate combustion salt, for example, a sodium carboxylate combustion salt or a potassium carboxylate combustion salt.

[0163] The carboxylate combustion salt may be an alkali metal acetate, an alkali metal citrate, or an alkali metal succinate.

[0164] For example, the method may include forming a combustible heat source that includes potassium citrate.

[0165] The method can include forming a combustible heat source that includes a single carboxylate combustion salt.

[0166] The method may include forming a combustible heat source comprising a combination of two or more different carboxylate salts. The two or more different carboxylate salts may comprise different carboxylate anions. The two or more different carboxylate salts may comprise different cations. For example, the method may include forming a combustible heat source comprising a combination of an alkali metal citrate and an alkaline earth metal succinate.

[0167] The method can include forming a combustible heat source including at least about 0.1 weight percent of one or more carboxylate combustion salts, at least about 0.5 weight percent of one or more carboxylate combustion salts, or at least about 1 weight percent of one or more carboxylate combustion salts.

[0168] The method may include forming a combustible heat source including about 4 percent by weight or less of one or more carboxylate combustion salts, or about 3 percent by weight or less of one or more carboxylate combustion salts.

[0169] The method can include forming a combustible heat source including about 0.1 weight percent to about 4 weight percent of one or more carboxylate combustion salts, or about 0.1 weight percent to about 3 weight percent of one or more carboxylate combustion salts.

[0170] The method can include forming a combustible heat source including about 0.5 weight percent to about 4 weight percent of one or more carboxylate combustion salts, or about 0.5 weight percent to about 3 weight percent of one or more carboxylate combustion salts.

[0171] The method can include forming a combustible heat source including about 1 weight percent to about 4 weight percent of one or more carboxylate combustion salts, or about 1 weight percent to about 3 weight percent of one or more carboxylate combustion salts.

[0172] Preferably, the method includes forming a substantially homogeneous combustible heat source in the composition.

[0173] The method may include forming the combustible heat source by combining one or more carbon materials, a binder, and any other components of the combustible heat source to form a mixture, and forming the mixture into a desired shape.

[0174] Preferably, the method includes combining one or more carbon materials, a binder, and any other components of the combustible heat source to form a granular mixture, and forming the granular mixture into a desired shape to form the combustible heat source.

[0175] More preferably, the method includes combining one or more carbon materials, a binder, and any other components of the combustible heat source to form a granular mixture, wherein the binder is dispersed in intergranular and intragranular locations, and forming the granular mixture into a desired shape to form the combustible heat source.

[0176] The method may include forming the combustible heat source by combining one or more carbon materials, a binder, and any other components of the combustible heat source using any suitable known method, such as, for example, dry granulation, wet granulation, high shear mixing, spheronization, or extrusion.

[0177] Preferably, the method includes forming the combustible heat source by combining one or more carbon materials, a binder, and any other components of the combustible heat source to form a granular mixture by dry granulation or wet granulation.

[0178] More preferably, the method includes forming the combustible heat source by combining one or more carbon materials, a binder, and any other components of the combustible heat source to form a granular mixture by wet granulation.

[0179] The method may include forming the mixture into the desired shape using any suitable known ceramic forming method, such as, for example, casting, extrusion, injection molding, and molding or pressing.

[0180] Preferably, the method involves forming the mixture into the desired shape by pressing or extrusion.

[0181] More preferably, the method may include forming the mixture into the desired shape by pressing.

[0182] The method includes heating the formed combustible heat source to a temperature of at least about 90 degrees Celsius.

[0183] The method may include heating the formed combustible heat source using any suitable known heating device. Suitable heating devices are known in the art and include, but are not limited to, conveyor drying ovens, dynamic drying ovens, and static drying ovens.

[0184] The method may include heating the formed combustible in air, in an inert atmosphere, or under vacuum.

[0185] Preferably, the method includes heating the formed combustible heat source in air.

[0186] Preferably, the method includes heating the formed combustible heat source at a temperature of at least about 100 degrees Celsius.

[0187] More preferably, the method includes heating the formed combustible heat source to a temperature of at least about 110 degrees Celsius.

[0188] The method may include heating the formed combustible heat source at a temperature of about 150 degrees Celsius or less.

[0189] Preferably, the method includes heating the formed combustible heat source at a temperature of about 140 degrees Celsius or less.

[0190] More preferably, the method includes heating the formed combustible heat source at a temperature of about 130 degrees Celsius or less.

[0191] The method may include heating a combustible heat source to a temperature of about 90 degrees Celsius to about 150 degrees Celsius, about 90 degrees Celsius to about 140 degrees Celsius, or about 90 degrees Celsius to about 130 degrees Celsius.

[0192] Preferably, the method includes heating the combustible heat source to a temperature of about 100 degrees Celsius to about 150 degrees Celsius, about 100 degrees Celsius to about 140 degrees Celsius, or about 100 degrees Celsius to about 130 degrees Celsius.

[0193] More preferably, the method comprises heating the combustible heat source to a temperature of about 110 degrees Celsius to about 150 degrees Celsius, about 110 degrees Celsius to about 140 degrees Celsius, or about 110 degrees Celsius to about 130 degrees Celsius.

[0194] The method includes heating the formed combustible heat source for at least about 45 minutes.

[0195] Preferably, the method includes heating the formed combustible heat source for at least about 60 minutes.

[0196] More preferably, the method includes heating the formed combustible heat source for at least about 90 minutes.

[0197] The method can include heating the formed combustible heat source for at least about 2 hours.

[0198] The method includes heating the formed combustible heat source for at least about 45 minutes.

[0199] Preferably, the method includes heating the formed combustible heat source for a period of about 32 hours or less.

[0200] More preferably, the method includes heating the formed combustible heat source for a period of about 24 hours or less.

[0201] The method may include heating the formed combustible heat source for a period of about 16 hours or less.

[0202] The method can include heating the combustible heat source for about 45 minutes to about 32 hours, about 45 minutes to about 24 hours, or about 45 minutes to about 16 hours.

[0203] Preferably, the method comprises heating the combustible heat source for about 60 minutes to about 32 hours, about 60 minutes to about 24 hours, or about 60 minutes to about 16 hours.

[0204] More preferably, the method comprises heating the combustible heat source for about 90 minutes to about 32 hours, about 90 minutes to about 24 hours, or about 90 minutes to about 16 hours.

[0205] The method can include heating the combustible heat source for about 2 hours to about 32 hours, about 2 hours to about 24 hours, or about 2 hours to about 16 hours.

[0206] After heating the formed combustible heat source to a temperature of at least about 90 degrees Celsius for at least about 45 minutes, the method can include passively cooling the combustible heat source to room temperature.

[0207] For example, if the method includes heating the formed combustible heat source in an oven at a temperature of at least about 90 degrees Celsius for at least about 45 minutes, the method may include turning off the oven and allowing the oven and combustible heat source to cool to room temperature.

[0208] Alternatively, if the method includes heating the formed combustible heat source in an oven at a temperature of at least about 90 degrees Celsius for at least about 45 minutes, the method may include removing the combustible heat source from the oven and cooling the combustible heat source to room temperature.

[0209] After heating the formed combustible heat source to a temperature of at least about 90 degrees Celsius for at least about 45 minutes, the method can include actively cooling the combustible heat source to room temperature.

[0210] For example, if the method includes heating the formed combustible heat source in an oven at a temperature of at least about 90 degrees Celsius for at least about 45 minutes, the method may include removing the combustible heat source from the oven and quenching the combustible heat source.

[0211] The rate of cooling of the combustible heat source to room temperature can be selected to result in increased crystallinity of the polyvinyl alcohol in the resulting combustible heat source.

[0212] Without intending to be bound by theory, it is believed that a higher cooling rate of the combustible heat source may advantageously promote increased crystallinity of the polyvinyl alcohol in the produced combustible heat source compared to a lower cooling rate.

[0213] As used herein in connection with the present invention, the terms "distal," "upstream," "forward," and "proximal," "downstream," and "rearward" are used to describe the relative positions of components or portions of components of an aerosol-generating article according to the present invention, including a combustible heat source produced by a method according to the present invention. An aerosol-generating article according to the present invention comprises a proximal end through which aerosol exits the aerosol-generating article for delivery to a user during use. The proximal end of the aerosol-generating article may also be referred to as the mouth end of the aerosol-generating article. During use, a user draws on the proximal end of the aerosol-generating article to inhale the aerosol generated by the aerosol-generating article.

[0214] The aerosol-generating article according to the present invention has a distal end. The combustible heat source produced by the method according to the present invention is located at or adjacent to the distal end of the aerosol-generating article. The mouth end of the aerosol-generating article is downstream of the distal end of the aerosol-generating article. The proximal end of the aerosol-generating article may also be referred to as the downstream end of the aerosol-generating article, and the distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article. Components or portions of components of the aerosol-generating article according to the present invention may be described as being upstream or downstream of each other based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article.

[0215] The combustible heat source produced by the method of the present invention has a front end face and a rear end face. The front end face of the combustible heat source is at the upstream end of the combustible heat source. The upstream end of the combustible heat source is the end of the combustible heat source that is farthest from the proximal end of the aerosol-generating article. The rear end face of the combustible heat source is at the downstream end of the combustible heat source. The downstream end of the combustible heat source is the end of the combustible heat source that is closest to the proximal end of the aerosol-generating article.

[0216] As used herein in connection with the present invention, the term "longitudinal direction" is used to describe the direction between the upstream and downstream ends of the aerosol-generating articles according to the present invention and the combustible heat sources produced by the methods according to the present invention.

[0217] As used herein in connection with the present invention, the term "transverse direction" is used to describe a direction perpendicular to the longitudinal axis, i.e., perpendicular to the direction between the upstream and downstream ends of the combustible heat source produced by the method of the present invention and the aerosol-generating article of the present invention.

[0218] As used herein in connection with the present invention, the term "length" is used to describe the maximum dimension along the major axis of the aerosol-generating article according to the present invention and the combustible heat source produced by the method according to the present invention.

[0219] As used herein in connection with the present invention, the term "diameter" is used to describe the largest transverse dimension of the aerosol-generating articles according to the present invention and the combustible heat sources produced by the methods according to the present invention.

[0220] The method may include forming a combustible heat source having any desired length.

[0221] The combustible heat source produced by the method according to the present invention can have a length of from about 5 millimeters to about 20 millimeters.

[0222] The combustible heat source produced by the method of the present invention preferably has a length of from about 7 millimeters to about 17 millimeters.

[0223] More preferably, the combustible heat source produced by the method according to the present invention has a length of from about 7 millimeters to about 15 millimeters.

[0224] Most preferably, the combustible heat source produced by the method of the present invention has a length of from about 7 millimeters to about 13 millimeters.

[0225] The method may include forming a combustible heat source having any desired diameter.

[0226] Combustible heat sources produced by methods according to the present invention can have a diameter of from about 5 millimeters to about 15 millimeters.

[0227] The combustible heat source produced by the method of the present invention preferably has a diameter of about 5 millimeters to about 10 millimeters.

[0228] More preferably, the combustible heat source produced by the method according to the present invention has a diameter of about 7 millimeters to about 8 millimeters.

[0229] For example, a combustible heat source made by a method according to the present invention may be tapered such that the diameter of the rear portion of the combustible heat source is greater than the diameter of the front portion of the combustible heat source.

[0230] The combustible heat source produced by the method according to the present invention is preferably of substantially uniform diameter.

[0231] Preferably, the combustible heat source produced by the method according to the invention is of substantially circular transverse cross section.

[0232] The combustible heat source produced by the method according to the invention is preferably substantially cylindrical in shape.

[0233] The combustible heat source produced by the method of the present invention can have a mass of about 300 milligrams to about 500 milligrams. For example, the combustible heat source produced by the method of the present invention has a mass of about 400 milligrams to about 450 milligrams.

[0234] The combustible heat source produced by the method according to the present invention may have an apparent density of from about 0.6 grams per cubic centimeter to about 1.0 grams per cubic centimeter.

[0235] Combustible heat sources made by methods according to the present invention can have a porosity of from about 20 percent to about 80 percent as measured, for example, by mercury porosimetry or helium pycnometry.

[0236] For example, a combustible heat source made by a method according to the present invention may have a porosity of about 20 percent to about 60 percent, about 50 percent to about 70 percent, or about 50 percent to about 60 percent, as measured, for example, by mercury porosimetry or helium pycnometry.

[0237] The desired porosity may be readily achieved during the formation of the combustible heat source made by the method according to the present invention using conventional methods and techniques.

[0238] The method may include forming a non-blind combustible heat source.

[0239] As used herein in connection with the present invention, the term "non-blind" is used to describe a combustible heat source that includes at least one airflow channel extending along the length of the combustible heat source through which air may pass for inhalation by a user.

[0240] When the combustible heat source is a non-blind combustible heat source, the aerosol-generating article may comprise a non-combustible, substantially non-blind barrier between the non-blind combustible heat source and the at least one airflow channel.

[0241] As used herein in connection with the present invention, the term "non-flammable barrier" is used to describe a barrier that is substantially non-flammable at the temperatures reached by a combustible heat source during its ignition and combustion.

[0242] By including a non-combustible, substantially non-permeable barrier between the non-blind combustible heat source and the at least one airflow channel, in use, combustion and decomposition products formed during ignition and combustion of the non-blind combustible heat source may advantageously be substantially prevented or inhibited from entering air drawn through the at least one airflow channel.

[0243] In use, the inclusion of a non-flammable, substantially non-breathable barrier between the non-blind, combustible heat source and the at least one airflow channel may advantageously substantially prevent or inhibit activation of combustion of the non-blind, combustible heat source during a puff by a user. When used in an aerosol-generating article according to the present invention, this may advantageously substantially prevent or inhibit a rapid increase in temperature of the aerosol-forming substrate of the aerosol-generating article during a puff by a user.

[0244] The barrier between the non-blind combustible heat source and the at least one airflow channel may have a low thermal conductivity or a high thermal conductivity.

[0245] The thickness of the barrier between the non-blind combustible heat source and the at least one airflow channel can be selected to achieve good performance.

[0246] The barrier between the non-blind combustible heat source and the at least one airflow channel may be formed from one or more suitable materials that are substantially thermally stable and non-combustible at temperatures reached by the non-blind combustible heat source during its ignition and combustion. Suitable materials are known in the art and include, but are not limited to, clays, metal oxides such as iron oxide, alumina, titania, silica, silica-alumina, zirconia and ceria, zeolites, zirconium phosphate, and other ceramic materials, or any combination thereof.

[0247] The barrier between the non-blind combustible heat source and the at least one airflow channel may be adhered or affixed to the inside surface of the at least one airflow channel of the non-blind combustible heat source.

[0248] Suitable methods for adhering or affixing a barrier to the inner surface of at least one airflow channel of a non-blind combustible heat source are known in the art and include, but are not limited to, those described in US 5,040,551 and WO 2009 / 074870 A2.

[0249] The barrier between the non-blind combustible heat source and the at least one airflow channel may comprise a liner inserted within the at least one airflow channel.

[0250] Preferably, the method includes forming a blind combustible heat source.

[0251] As used herein in connection with the present invention, the term "blind" is used to describe a combustible heat source that does not include an airflow channel extending along the length of the combustible heat source through which air may be drawn for inhalation by a user.

[0252] Blind combustible heat sources made by methods according to the present invention, and non-blind combustible heat sources made by methods according to the present invention, may include one or more closed or blocked channels through which air may not be drawn upon inhalation by a user.

[0253] For example, the combustible heat source may include one or more enclosed passages that extend only partway along the length of the combustible heat source.

[0254] The inclusion of one or more enclosed channels can increase the surface area of ​​the combustible heat source exposed to oxygen from the air, which can advantageously facilitate ignition and sustained combustion of the combustible heat source.

[0255] An aerosol-generating article according to the present invention comprises a combustible heat source and an aerosol-forming substrate made by a method according to the present invention.

[0256] As used herein in connection with the present invention, the term "aerosol-forming substrate" is used to describe a substrate comprising an aerosol-forming material capable of releasing, upon heating, a volatile compound capable of forming an aerosol. The aerosol generated from an aerosol-forming substrate of an aerosol-generating article according to the present invention may or may not be visible and may comprise vapor (e.g., fine particles of a substance in a gaseous state, e.g., of a substance that is normally a liquid or solid at room temperature) as well as droplets of gas and condensed vapor.

[0257] The aerosol-forming substrate may be in the form of a plug or segment comprising a material capable of releasing a volatile compound upon heating, which can be surrounded by a packaging to form an aerosol. When the aerosol-forming substrate is in the form of such a plug or segment, the entire plug or segment, including the packaging, is considered to be the aerosol-forming substrate.

[0258] The aerosol-forming substrate may be located downstream of the combustible heat source, i.e., the aerosol-forming substrate is located between the combustible heat source and the distal end of the aerosol-generating article.

[0259] The aerosol-forming substrate may be adjacent to a combustible heat source.

[0260] The aerosol-forming substrate may be longitudinally spaced from the combustible heat source.

[0261] Advantageously, the aerosol-forming substrate comprises an aerosol-forming material comprising an aerosol former.

[0262] The aerosol former may be any suitable compound or mixture of compounds that facilitates the formation of a dense, stable aerosol during use and that is substantially resistant to thermal decomposition at the operating temperature of the aerosol-generating article. Suitable aerosol formers are known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, propylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol mono-, di-, or triacetate), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate and tetradecanedioate).

[0263] Advantageously, the aerosol former comprises one or more polyhydric alcohols.

[0264] More advantageously, the aerosol former comprises glycerin.

[0265] The aerosol-forming substrate is preferably a solid aerosol-forming substrate. The aerosol-forming substrate may comprise both solid and liquid components.

[0266] The aerosol-forming substrate may comprise a plant-derived material.The aerosol-forming substrate may comprise a homogenized plant-derived material.

[0267] The aerosol-forming substrate may comprise nicotine.

[0268] The aerosol-forming substrate may comprise a tobacco material.

[0269] As used herein in connection with the present invention, the term "tobacco material" is used to describe any material containing tobacco, including, but not limited to, tobacco leaves, tobacco ribs, tobacco stems, tobacco trunks, tobacco dust, expanded tobacco, reconstituted tobacco material, and homogenized tobacco material.

[0270] The tobacco material may be in the form of, for example, powder, granules, pellets, pieces, strands, strips, sheets, or any combination thereof.

[0271] Advantageously, the aerosol-forming substrate comprises homogenized tobacco material.

[0272] As used herein in connection with the present invention, the term "homogenized tobacco" is used to describe a material formed by agglomerating particulate tobacco.

[0273] In certain embodiments, the aerosol-forming substrate advantageously comprises a plurality of strands of homogenized tobacco material.

[0274] Advantageously, the plurality of strands of homogenized tobacco material may be aligned substantially parallel to one another within the aerosol-forming substrate.

[0275] In certain embodiments, the aerosol-forming substrate advantageously comprises an assemblage of sheets of homogenized tobacco material.

[0276] The aerosol-forming substrate may comprise a rod comprising an assemblage of sheets of homogenized tobacco material.

[0277] As used herein in connection with the present invention, the term "rod" is used to describe a substantially cylindrically shaped element of substantially circular, oval or elliptical cross section.

[0278] As used herein in connection with the present invention, the term "sheet" is used to describe a laminar element having a width and length that is significantly greater than its thickness.

[0279] As used herein in connection with the present invention, the term "collected" is used to describe a sheet that is rolled, folded, or otherwise compressed or contracted in a direction substantially transverse to the longitudinal axis of the aerosol-generating article.

[0280] The aerosol-forming substrate may comprise an aerosol-forming material and a packaging that surrounds and contacts the aerosol-forming material.

[0281] The wrapper may be formed from any suitable sheet material that can be wrapped around the aerosol-forming material to form the aerosol-forming substrate.

[0282] In certain embodiments, the aerosol-forming substrate may comprise a rod comprising an assemblage of sheets of homogenized tobacco material, and a wrapper surrounding and in contact with the tobacco material.

[0283] In certain embodiments, the aerosol-forming substrate advantageously comprises an assemblage of textured sheets of homogenized tobacco material.

[0284] As used herein in connection with the present invention, the term "textured sheet" is used to describe a sheet that is crimped, embossed, debossed, perforated, or deformed.

[0285] The use of textured sheets of homogenized tobacco material may advantageously facilitate assembling the homogenized tobacco material sheets to form the aerosol-forming substrate.

[0286] The aerosol-forming substrate may comprise an assembly of a textured sheet of homogenized tobacco material containing a plurality of spaced indentations, protrusions, perforations or any combination thereof.

[0287] The aerosol-forming substrate may comprise an assemblage of crimped sheets of homogenized tobacco material.

[0288] As used herein in connection with the present invention, the term "crimped sheet" is used to describe a sheet having a plurality of substantially parallel ridges or corrugations.

[0289] Advantageously, when an aerosol-generating article according to the invention comprising an aerosol-forming substrate is assembled, the substantially parallel ridges or corrugations extend along or parallel to the longitudinal axis of the aerosol-generating article, which facilitates assembly of the crimped sheet of homogenized tobacco material to form the aerosol-forming substrate.

[0290] However, it will be appreciated that a crimped sheet of homogenized tobacco material for inclusion in an aerosol-forming substrate of an aerosol-generating article according to the present invention may alternatively or additionally have a plurality of substantially parallel ridges or corrugations that are disposed at acute or obtuse angles to the longitudinal axis of the aerosol-generating article when the aerosol-generating article is assembled.

[0291] The aerosol-forming substrate is preferably substantially cylindrical in shape.

[0292] The aerosol-forming substrate may have a length of from about 5 millimeters to about 20 millimeters.

[0293] The aerosol-forming substrate preferably has a length of from about 6 millimeters to about 15 millimeters.

[0294] More preferably, the aerosol-forming substrate has a length of from about 7 millimeters to about 12 millimeters.

[0295] The aerosol-forming substrate may have an outer diameter of from about 5 millimeters to about 15 millimeters.

[0296] The aerosol-forming substrate preferably has a length of about 5 mm to about 10 mm.

[0297] More preferably, the aerosol-forming substrate has a length of about 7 mm to about 8 mm.

[0298] Aerosol-generating articles according to the present invention may comprise a combustible heat source made by a method according to the present invention, an aerosol-forming substrate and one or more other components.

[0299] An aerosol-generating article according to the present invention may comprise a combustible heat source made by a method according to the present invention, an aerosol-forming substrate downstream of the combustible heat source, and one or more other components.

[0300] The combustible heat source, the aerosol-forming substrate, and, if included, one or more other components are assembled within one or more packages of the aerosol-generating article to form an elongated rod having a proximal end and an opposed distal end, and in this manner, the aerosol-generating article according to the present invention is similar to a conventional cigarette with a lit end.

[0301] The one or more other components may include one or more of a cap, a moving or spacer element, an aerosol cooling element, or a heat exchanger and a mouthpiece.

[0302] An aerosol-generating article according to the present invention may include a cap configured to at least partially cover a front portion of a combustible heat source produced by a method according to the present invention. The cap is removable, thereby exposing the front portion of the combustible heat source prior to use of the aerosol-generating article. The cap advantageously protects the combustible heat source prior to use of the aerosol-generating article.

[0303] As used herein in connection with the present invention, the term "cap" is used to describe a protective cover at the distal end of an aerosol-generating article that substantially encloses the forward portion of the combustible heat source.

[0304] For example, an aerosol-generating article according to the present invention may include a removable cap attached to the distal end of the aerosol-generating article at a line of weakness, the cap comprising a cylindrically shaped plug of material surrounded by packaging, as described in WO2014 / 086998A1.

[0305] The aerosol-generating article according to the present invention may comprise a moving or spacer element downstream of the aerosol-forming substrate, i.e. the moving or spacer element is located between the aerosol-forming substrate and the proximal end of the aerosol-generating article.

[0306] The transfer element may be adjacent to the aerosol-forming substrate, or alternatively, the transfer element may be longitudinally spaced from the aerosol-forming substrate.

[0307] The inclusion of a moving element may advantageously allow for cooling of the generated aerosol by heat transfer from the combustible heat source to the aerosol-forming substrate.

[0308] The inclusion of a transfer element may also advantageously allow the overall length of the aerosol-generating article to be adjusted to a desired value by appropriate selection of the length of the transfer element, for example, the inclusion of a transfer element allows the overall length of the aerosol-generating article to be adjusted to a length similar to that of a conventional cigarette.

[0309] The moving element may have a length of about 7 millimeters to about 50 millimeters. For example, the moving element may have a length of about 10 millimeters to about 45 millimeters, or about 15 millimeters to about 30 millimeters.

[0310] The transfer element may have other lengths depending on the desired overall length of the aerosol-generating article and the presence and lengths of other components within the aerosol-generating article.

[0311] The transfer element may comprise at least one open-ended tubular hollow body. In use, air drawn into the aerosol-generating article by a user may pass through the open-ended tubular hollow body as it passes downstream through the aerosol-generating article from the aerosol-forming substrate to the proximal end of the aerosol-generating article.

[0312] The open-ended tubular hollow body may be formed from one or more suitable materials that are substantially thermally stable at the temperature of the aerosol generated by the transfer of heat from the combustible heat source to the aerosol-forming substrate. Suitable materials are known in the art and include, but are not limited to, paper, cardboard, thermoplastics such as cellulose acetate, ceramics, and combinations thereof.

[0313] The aerosol-generating article according to the present invention may comprise an aerosol-cooling element or heat exchanger downstream of the aerosol-forming substrate, i.e., the aerosol-cooling element or heat exchanger is located between the aerosol-forming substrate and the proximal end of the aerosol-generating article.

[0314] The aerosol cooling element can advantageously cool the aerosol generated by heat transfer from a combustible heat source to an aerosol-forming substrate.

[0315] The aerosol cooling element may include a plurality of longitudinally extending channels.

[0316] The aerosol cooling element may comprise an assembly of sheets of material selected from the group consisting of metal foil, polymeric material, and substantially non-porous paper or cardboard.

[0317] The aerosol cooling element may comprise an assembly of sheets of material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), cellulose acetate (CA), and aluminum foil.

[0318] The aerosol cooling element may comprise an assembly of sheets of biodegradable polymeric material such as polylactic acid (PLA) or Mater-Bi® grades (a family of commercially available starch-based copolyesters).

[0319] When the aerosol-generating article according to the invention comprises a moving element downstream of the aerosol-forming substrate and an aerosol-cooling element downstream of the aerosol-forming substrate, the aerosol-cooling element is preferably downstream of the moving element, i.e., the aerosol-cooling element is preferably located between the moving element and the proximal end of the aerosol-generating article.

[0320] The aerosol-generating article according to the present invention may comprise a mouthpiece downstream of the aerosol-forming substrate, i.e. the mouthpiece is located between the aerosol-forming substrate and the proximal end of the aerosol-generating article.

[0321] Aerosol-generating articles according to the present invention preferably include a mouthpiece located at the proximal end of the aerosol-generating article.

[0322] The mouthpiece may have low or very low filtering efficiency.

[0323] The mouthpiece may be a single segment mouthpiece.

[0324] The mouthpiece may be a multi-segment mouthpiece.

[0325] The mouthpiece may include one or more segments containing filtering material.

[0326] Suitable filter materials are known in the art and include, but are not limited to, cellulose acetate and paper.

[0327] The mouthpiece may comprise one or more segments containing absorbent material.

[0328] The mouthpiece may include one or more segments containing an adsorbent material.

[0329] Suitable absorbent materials and suitable adsorbent materials are known in the art and include, but are not limited to, activated carbon, silica gel, and zeolites.

[0330] Aerosol-generating articles according to the present invention may include one or more aerosol modifiers downstream of the aerosol-forming substrate. For example, if included, one or more of the mouthpiece, transfer element, and aerosol-cooling element of an aerosol-generating article according to the present invention may include one or more aerosol modifiers.

[0331] As used herein in connection with the present invention, the term "aerosol modifier" is used to describe an agent that, in use, modifies one or more characteristics or properties of the aerosol generated by the aerosol-forming substrate of the aerosol-generating article.

[0332] Suitable aerosol modifiers include, but are not limited to, flavoring agents, and chemosensory agents.

[0333] As used herein in connection with the present invention, the term "chemosensory agent" is used to describe an agent that, when used, is perceived in the oral or nasal cavity of a user by means other than, or in addition to, perception via taste or olfactory receptor cells. Perception of chemosensory agents is typically via a "trigeminal response," i.e., via either the trigeminal nerve, glossopharyngeal nerve, or vagus nerve, or some combination thereof. Chemosensory agents are typically perceived as having a hot, savory, cooling, or calming sensation.

[0334] Aerosol-generating articles according to the present invention may include one or more aerosol modifiers downstream of the aerosol-forming substrate that are both flavorants and chemosensory agents. For example, if included, one or more of the mouthpiece, transfer element, and aerosol-cooling element of an aerosol-generating article according to the present invention may include menthol or another flavorant that provides a cooling chemosensory effect.

[0335] Aerosol-generating articles according to the present invention may comprise one or more thermally conductive elements.

[0336] Preferably, the aerosol-generating article according to the invention comprises a thermally conductive element around at least a portion of the aerosol-forming substrate, which advantageously transfers heat to the periphery of the aerosol-forming substrate by conduction.

[0337] More preferably, the aerosol-generating article according to the invention comprises a thermally conductive element surrounding and in contact with at least a portion of the aerosol-forming substrate, which may advantageously facilitate conductive heat transfer to the periphery of the aerosol-forming substrate.

[0338] The thermally conductive element may be around the entire length of the aerosol-forming substrate, i.e. the thermally conductive element may be on the entire length of the aerosol-forming substrate.

[0339] Preferably, the thermally conductive element is absent around the rear portion of the aerosol-forming substrate, i.e. the aerosol-forming substrate advantageously extends longitudinally in the downstream direction beyond the thermally conductive element.

[0340] Preferably, the aerosol-forming substrate extends longitudinally at least about 3 millimeters in the downstream direction beyond the thermally conductive element.

[0341] Preferably, an aerosol-generating article according to the present invention comprises a thermally conductive element around at least a portion of the combustible heat source and around at least a portion of the aerosol-forming substrate.

[0342] More preferably, an aerosol-generating article according to the present invention comprises a heat-conductive element around at least a rear portion of the combustible heat source and around at least a front portion of the aerosol-forming substrate.

[0343] Most preferably, an aerosol-generating article according to the present invention comprises a thermally conductive element around and in contact with at least a rear portion of the combustible heat source and around and in contact with at least a front portion of the aerosol-forming substrate.

[0344] The thermally conductive element may provide a thermal link between the combustible heat source and the aerosol-forming substrate of the aerosol-generating article, which may advantageously help to facilitate adequate heat transfer from the combustible heat source to the aerosol-forming substrate to produce an acceptable aerosol.

[0345] Preferably, the rear portion of the heat source in contact with the thermally conductive element is between about 2 millimeters and about 8 millimeters in length.

[0346] More preferably, the rear portion of the heat source in contact with the thermally conductive element is between about 3 millimeters and about 5 millimeters.

[0347] The thermally conductive element is preferably non-flammable.

[0348] The thermally conductive element may be oxygen-restrictive, in other words, the thermally conductive element may inhibit or prevent the passage of oxygen through the thermally conductive element.

[0349] The thermally conductive element may be formed from any suitable thermally conductive material or combination of materials.

[0350] The thermally conductive element preferably comprises one or more thermally conductive materials having a bulk thermal conductivity of about 10 Watts per meter Kelvin (W / (m·K)) to about 500 Watts per meter Kelvin (W / (m·K)), and more preferably, about 15 Watts per meter Kelvin (W / (m·K)) to about 400 Watts per meter Kelvin (W / (m·K)), at 23 degrees Celsius and 50 percent relative humidity, as measured using a modified transient plane source (MTPS).

[0351] Advantageously, the thermally conductive element comprises one or more metals, one or more alloys, or a combination of one or more metals and one or more alloys.

[0352] Suitable thermally conductive materials are known in the art and include, but are not limited to, metal foils such as aluminum foil, iron foil and copper foil, and alloy foils such as steel foil.

[0353] Advantageously, the thermally conductive element comprises aluminium foil.

[0354] An aerosol-generating article according to the present invention may comprise a non-combustible, substantially non-permeable barrier between the rear end face of the combustible heat source and the aerosol-forming substrate.

[0355] By including a non-flammable, substantially non-permeable barrier between the rear end face of the combustible heat source and the aerosol-forming substrate, the temperature to which the aerosol-forming substrate is exposed during ignition and combustion of the combustible heat source may be advantageously reduced, which may help to avoid or reduce thermal decomposition or combustion of the aerosol-forming substrate during use of the aerosol-generating article.

[0356] By including a non-flammable, substantially non-permeable barrier between the rear end face of the combustible heat source and the aerosol-forming substrate, migration of components of the aerosol-forming substrate to the combustible heat source can advantageously be substantially prevented or inhibited during storage and use of the aerosol-generating article.

[0357] The barrier may be adjacent to one or both of the rear end face of the combustible heat source and the aerosol-forming substrate, or the barrier may be longitudinally spaced from one or both of the rear end face of the combustible heat source and the aerosol-forming substrate.

[0358] Advantageously, the barrier is glued or affixed to the rear end face of the combustible heat source.

[0359] Suitable methods for adhering or affixing a barrier to the rear end face of a combustible heat source are known in the art and include, but are not limited to, spray painting, vapor deposition, dipping, material transfer (e.g., brushing or gluing), electrostatic deposition, pressure application, or any combination thereof.

[0360] The barrier between the back end face of the combustible heat source and the aerosol-forming substrate may have a low or high thermal conductivity. For example, the barrier may be formed from a material having a bulk thermal conductivity of about 0.1 Watts per meter Kelvin (W / (m K)) to about 200 Watts per meter Kelvin (W / (m K)) at 23 degrees Celsius and 50 percent relative humidity when measured using the modified transient plane heat source (MTPS) method.

[0361] The thickness of the barrier between the back face of the combustible heat source and the aerosol-forming substrate can be selected to achieve good performance, for example, the thickness of the barrier can be from about 10 micrometers to about 500 micrometers.

[0362] The barrier between the back end face of the combustible heat source and the aerosol-forming substrate may be formed from one or more suitable materials that are substantially thermally stable and non-flammable at the temperatures reached by the combustible heat source during its ignition and combustion. Suitable materials are known in the art and include, but are not limited to, clays such as bentonite and kaolinite, glasses, minerals, ceramic materials, resins, metals, or any combination thereof.

[0363] Preferably, the barrier comprises aluminum foil.

[0364] The aluminum foil barrier may be applied to the rear end face of the combustible heat source by gluing or pressing it to the combustible heat source. The barrier may be cut or otherwise machined so that the aluminum foil covers and adheres to at least substantially the entire rear end face of the combustible heat source. Advantageously, the aluminum foil covers and adheres to the entire rear end face of the combustible heat source.

[0365] Aerosol-generating articles according to the present invention may include a non-blind combustible heat source made by a method according to the present invention.

[0366] Where the combustible heat source is a blind combustible heat source, in use, air drawn through the aerosol-generating article for inhalation by a user passes through at least one airflow channel along the length of the combustible heat source.

[0367] When the combustible heat source is a non-blind combustible heat source, heating of the aerosol-forming substrate occurs by conduction and forced convection.

[0368] When an aerosol-generating article according to the present invention comprises a non-blind combustible heat source made by a method according to the present invention and a non-combustible, substantially non-permeable barrier between the rear end face of the combustible heat source and the aerosol-forming substrate, the barrier should allow air drawn through at least one airflow channel extending along the length of the combustible heat source to be drawn downstream through the aerosol-generating article.

[0369] Aerosol-generating articles according to the present invention preferably include a blind combustible heat source made by a method according to the present invention.

[0370] If the combustible heat source is a blind combustible heat source, in use, air drawn through the aerosol-generating article due to inhalation by a user does not pass through any airflow channels along the length of the blind combustible heat source.

[0371] If the combustible heat source is a blind combustible heat source, heating of the aerosol-forming substrate occurs primarily by conduction and heating of the aerosol-forming substrate by forced convection is minimized or reduced. In such embodiments, it is particularly important to optimize conductive heat transfer between the combustible heat source and the aerosol-forming substrate.

[0372] The lack of any airflow channels extending along the length of the combustible heat source through which air may be drawn for inhalation by a user advantageously substantially prevents or inhibits activation of combustion of the blind combustible heat source during a user puff, which may advantageously substantially prevent or inhibit a rapid rise in the temperature of the aerosol-forming substrate during a user puff.

[0373] By preventing or inhibiting activation of combustion of blind combustible heat sources, and thus preventing or inhibiting excessive temperature rise in the aerosol-forming substrate, combustion or thermal decomposition of the aerosol-forming substrate under heavy puffing conditions can be advantageously avoided. Additionally, the impact of the user's puffing conditions on the composition of the mainstream aerosol can be advantageously minimized or reduced.

[0374] The inclusion of a blind combustible heat source may advantageously substantially prevent or inhibit combustion and decomposition products and other materials formed during ignition and combustion of the blind combustible heat source from entering air drawn through the aerosol-generating article for inhalation by the user.

[0375] When the combustible heat source is a blind combustible heat source, the aerosol-generating article according to the present invention includes one or more air intakes downstream of the blind combustible heat source that draw air into the aerosol-generating article for inhalation by a user.

[0376] In such an embodiment, air drawn through the aerosol-generating article for inhalation by a user enters the aerosol-generating article through one or more air inlets rather than through the distal end of the aerosol-generating article.

[0377] Where the combustible heat source is a non-blind combustible heat source, the aerosol-generating article according to the present invention may further include one or more air intakes downstream of the non-blind combustible heat source for drawing air into the aerosol-generating article for inhalation by a user.

[0378] Aerosol-generating articles according to the present invention may include one or more air inlets around the periphery of the aerosol-forming substrate.

[0379] In such an embodiment, during a puff by the user, cool air is drawn into the aerosol-forming substrate of the aerosol-generating article through one or more air inlets around the periphery of the aerosol-forming substrate, which advantageously reduces the temperature of the aerosol-forming substrate during a puff by the user, thereby substantially preventing or inhibiting a sudden increase in the temperature of the aerosol-forming substrate.

[0380] As used herein in connection with the present invention, the term "cool air" is used to describe ambient air that is not significantly heated by a combustible heat source during puffing by a user.

[0381] By preventing or inhibiting a rapid increase in the temperature of the aerosol-forming substrate, the inclusion of one or more air inlets around the periphery of the aerosol-forming substrate advantageously helps to avoid or reduce combustion or thermal decomposition of the aerosol-forming substrate under heavy smoking conditions.

[0382] The inclusion of one or more air inlets around the periphery of the aerosol-forming substrate advantageously serves to minimize or reduce the effect of the user's puffing conditions on the composition of the mainstream aerosol of the aerosol-generating article.

[0383] In certain preferred embodiments, the aerosol-generating article according to the present invention may comprise one or more air inlets located near the downstream end of the aerosol-forming substrate.

[0384] Aerosol-generating articles according to the present invention may have any desired length.

[0385] Preferably, aerosol-generating articles according to the present invention may have a length of from about 65 millimeters to about 100 millimeters.

[0386] Aerosol-generating articles according to the present invention may have any desired width.

[0387] Preferably, aerosol-generating articles according to the present invention may have a width of from about 5 millimeters to about 12 millimeters.

[0388] Aerosol-generating articles according to the present invention may be assembled using known methods and machinery.

[0389] For the avoidance of doubt, where applicable, the features described above in relation to the method according to the invention may also apply to the combustible heat source produced by the method according to the invention, and vice versa.

[0390] For the avoidance of doubt, where applicable, the features described above in relation to the combustible heat source made by the method according to the invention may also apply to the aerosol-generating article according to the invention, and vice versa.

[0391] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0392] [Figure 1] FIG. 1 shows a schematic longitudinal cross-section of an aerosol-generating article according to an embodiment of the present invention. [Figure 2] FIG. 2 shows the time it takes for the calcium peroxide content of a combustible heat source made by a method according to the present invention and a comparative combustible heat source made by a method not according to the present invention to reach a lower limit of 32.7 weight percent. [Figure 3]FIG. 3 shows the time it takes for the calcium peroxide content of a combustible heat source made by a method according to the present invention and a comparative combustible heat source made by a method not according to the present invention to reach the lower limit of 32.7 weight percent. DETAILED DESCRIPTION OF THE INVENTION

[0393] An aerosol-generating article 2 according to an embodiment of the present invention, shown in Figure 1, comprises a combustible heat source 4 produced by a method according to the present invention, and an aerosol-forming substrate 10 located downstream of the combustible heat source 4. The combustible heat source 4 is a blind combustible heat source having a front end surface 6 and an opposing rear end surface 8, and is located at the distal end of the aerosol-generating article 2. The aerosol-generating article 2 further comprises a moving element 12, an aerosol-cooling element 14, a spacer element 16, and a mouthpiece 18. The combustible heat source 4 is arranged such that the aerosol-forming substrate 10, the moving element 12, the aerosol-cooling element 14, the spacer element 16, and the mouthpiece 18 are adjacent and coaxially aligned. As shown in Figure 1, the aerosol-forming substrate 10, the moving element 12, the aerosol-cooling element 14, the spacer element 16, and the mouthpiece 18, as well as the rear portion of the combustible heat source 4, are wrapped in an outer wrapper 20 of a sheet material, such as cigarette paper.

[0394] 1, a non-combustible, substantially impermeable barrier 22 in the form of an aluminum foil disk is provided between the trailing end surface 8 of the combustible heat source 4 and the aerosol-forming substrate 10. The barrier 22 is applied to the trailing end surface 8 of the combustible carbonaceous heat source 4 by pressing the aluminum foil disk onto the trailing end surface 8 of the combustible heat source 4, adjacent the trailing end surface 8 of the combustible carbonaceous heat source 4 and the aerosol-forming substrate 10.

[0395] The combustible heat source 4 made by the method according to the present invention comprises carbon, a binder comprising a combination of carboxymethyl cellulose and polyvinyl alcohol, and an alkaline earth metal peroxide ignition aid.

[0396] The aerosol-forming substrate 10 is located immediately downstream of a barrier 22 applied to the rear end surface 8 of the combustible heat source 4. The aerosol-forming substrate 10 includes a collection 24 of crimped sheets of homogenized tobacco material and a wrapper 26 surrounding and in direct contact with the collection 24 of crimped sheets of homogenized tobacco material. The collection 24 of crimped sheets of homogenized tobacco material includes a suitable aerosol former, such as, for example, glycerin.

[0397] The transfer element 12 is located immediately downstream of the aerosol-forming substrate 10 and comprises a hollow, cylindrical, open-ended cellulose acetate tube 28 .

[0398] The aerosol cooling element 14 is located immediately downstream of the moving element 12 and comprises an assembly of sheets of a biodegradable polymeric material, such as polylactic acid.

[0399] Spacer element 16 is located immediately downstream of aerosol cooling element 14 and comprises a hollow, open-ended, cylindrical paper or cardboard tube.

[0400] Mouthpiece 18 is located immediately downstream of spacer element 16. As shown in Figure 1, mouthpiece 18 is located at the proximal end of aerosol-generating article 2 and includes a cylindrical plug 30 of suitable filtering material, such as very low filtering efficiency cellulose acetate tow, enclosed in a filter plug wrap 32.

[0401] The aerosol-generating article may further include a strip of tipping paper (not shown) surrounding the downstream end portion of the outer wrapper 20 .

[0402] As shown in FIG. 1 , the aerosol-generating article 2 further comprises a thermally conductive element 34 formed from a suitable thermally conductive material, such as aluminum foil, that surrounds and is in direct contact with the rear portion 4 b of the combustible heat source 4 and the front portion 10 a of the aerosol-forming substrate 10. In the aerosol-generating article 2 according to the embodiment of the present invention shown in FIG. 1 , the aerosol-forming substrate 10 extends downstream beyond the thermally conductive element 34. That is, the thermally conductive element 34 does not surround and is not in contact with the rear portion of the aerosol-forming substrate 10. However, it will be understood that in other embodiments of the present invention (not shown), the thermally conductive element 34 may surround and be in contact with the entire length of the aerosol-forming substrate 10. It will also be understood that in other embodiments of the present invention (not shown), one or more additional thermally conductive elements on top of the thermally conductive element 34 may also be provided.

[0403] The aerosol-generating article 2 according to an embodiment of the invention shown in Figure 1 includes one or more air inlet openings 36 around the periphery of the aerosol-forming substrate 10. As shown in Figure 1, a peripheral arrangement of air inlet openings 36 is provided in the packaging 26 of the aerosol-forming substrate 10 and the overlying outer packaging 20 to allow cool air (indicated by the dotted arrows in Figure 1) to enter the aerosol-forming substrate 10.

[0404] In use, a user ignites the combustible carbonaceous heat source 4. Once the combustible carbonaceous heat source 4 is ignited, the user draws on the mouthpiece 18 of the aerosol-generating article 2. As the user draws on the mouthpiece 18, cool air (indicated by the dotted arrow in FIG. 1 ) is drawn through the air inlet 36 and into the aerosol-forming substrate 10 of the aerosol-generating article 2.

[0405] The periphery of the front portion 10 a of the aerosol-forming substrate 10 is heated by conduction through the rear end face 8 of the combustible heat source 4 and the barrier 22 and the thermally conductive element 34 .

[0406] Heating of the aerosol-forming substrate 10 by conduction releases aerosol formers and other volatile and semi-volatile compounds from the assembly 24 of crimped sheets of homogenized tobacco material. As the compounds released from the aerosol-forming substrate 10 flow through the aerosol-forming substrate 10, they form an aerosol that is entrained in air drawn into the aerosol-forming substrate 10 of the aerosol-generating article 2 through the air inlet 36. The drawn-in air and entrained aerosol (indicated by dashed arrows in FIG. 1 ) pass downstream through the interior of the cylindrical, open-ended, hollow cellulose acetate tube 28 of the transfer element 12, the aerosol cooling element 14, and the spacer element 16, where they cool and condense. The cooled drawn-in air and entrained aerosol flow downstream through the mouthpiece 18 and are delivered to the user through the proximal end of the aerosol-generating article 2. A non-combustible, substantially non-permeable barrier 22 on the rear end face 8 of the combustible carbonaceous heat source 4 separates the combustible heat source 4 from air drawn through the aerosol-generating article 2 so that, in use, the air drawn through the aerosol-generating article 2 does not come into direct contact with the combustible heat source.

[0407] Examples (a)(i) to (a)(vii) A combustible heat source having the composition shown in Example (a) of Table 1 is formed by a method according to the present invention: [Table 1]

[0408] The ingredients in Example (a) of Table 1 are combined to form a granular mixture by wet granulation. Charcoal, calcium peroxide, and carboxymethyl cellulose are mixed to form a particle mixture. The particle mixture of charcoal, calcium peroxide, and carboxymethyl cellulose is air-fluidized and sprayed with an aqueous solution of polyvinyl alcohol to form a granular mixture.

[0409] The granular mixture is pressed into a cylindrical shape. Approximately 400 milligrams of the granular mixture is pressed into a single cavity press to form a cylindrically shaped combustible heat source having a length of approximately 9 millimeters, a diameter of approximately 7.7 millimeters, and a density of approximately 0.9 grams per cubic centimeter. The formed cylindrically shaped combustible heat source is removed from the single cavity press.

[0410] A formed cylindrical combustible heat source having the composition shown in Example (a) of Table 1 is heated in air in a ventilated drying oven at the temperatures shown in Examples (a)(i) to (a)(iv) of Table 2 for a period of 5 hours. [Table 2]

[0411] The combustible heat source is removed from the oven and allowed to cool to room temperature.

[0412] A formed cylindrically shaped combustible heat source having the composition shown in Example (a) of Table 1 is also heated in air in a ventilated drying oven at a temperature of 120 degrees Celsius for the period of time shown in Examples (a)(v) through (a)(vii) of Table 3. [Table 3]

[0413] The combustible heat source is removed from the oven and allowed to cool to room temperature.

[0414] Comparative Examples (b), (c)(i) and (c)(ii) Combustible heat sources having the compositions shown in Examples (b) and (c) of Table 1 are formed by methods not according to the present invention.

[0415] The ingredients in Example (b) of Table 1 are combined to form a granular mixture by wet granulation. Charcoal, calcium peroxide, and carboxymethyl cellulose are mixed to form a particle mixture. The particle mixture of charcoal, calcium peroxide, and carboxymethyl cellulose is air-fluidized and sprayed with an aqueous solution of polyvinyl alcohol to form a granular mixture.

[0416] The granular mixture is pressed into a cylindrical shape. Approximately 400 milligrams of the granular mixture is pressed into a single cavity press to form a cylindrically shaped combustible heat source having a length of approximately 9 millimeters, a diameter of approximately 7.7 millimeters, and a density of approximately 0.9 grams per cubic centimeter. The formed cylindrically shaped combustible heat source is removed from the single cavity press.

[0417] A cylindrically shaped combustible heat source formed with the composition shown in Example (b) of Table 1 is not heated as shown in Example (b) of Table 4.

[0418] The ingredients of Example (c) in Table 1 are combined to form a granular mixture by wet granulation. Charcoal, calcium peroxide, and carboxymethyl cellulose are mixed to form a particle mixture. The particle mixture of charcoal, calcium peroxide, and carboxymethyl cellulose is air-fluidized and sprayed with a liquid solution of tripotassium citrate hydrate followed by an aqueous solution of bentonite to form a granular mixture.

[0419] The granular mixture is pressed into a cylindrical shape. Approximately 400 milligrams of the granular mixture is pressed into a single cavity press to form a cylindrically shaped combustible heat source having a length of approximately 9 millimeters, a diameter of approximately 7.7 millimeters, and a density of approximately 0.9 grams per cubic centimeter. The formed cylindrically shaped combustible heat source is removed from the single cavity press.

[0420] A cylindrically shaped combustible heat source formed with the composition shown in Example (c) of Table 1 is not heated as shown in Example (c)(i) of Table 4.

[0421] A formed cylindrically shaped combustible heat source having the composition shown in Example (c) of Table 1 is heated in air in a ventilated drying oven at the temperature and for the period shown in Example (c)(ii) of Table 4. [Table 4]

[0422] The combustible heat source is removed from the oven and allowed to cool to room temperature.

[0423] To simulate environmental conditions to which the combustible heat sources may be exposed during shipping and storage, the combustible heat sources produced by methods according to the present invention in Examples (a)(i) through (a)(vii) and the comparative combustible heat sources produced by methods not according to the present invention in Examples (b), (c)(i), and (c)(ii) were conditioned at approximately 30 degrees Celsius and approximately 75 percent relative humidity. The calcium peroxide content of the combustible heat sources produced by methods according to the present invention and the comparative combustible heat sources produced by methods not according to the present invention was measured as a function of time by titration with potassium permanganate (KMnO) solution. The time it takes for the measured calcium peroxide content of the combustible heat sources produced by methods according to the present invention and the comparative combustible heat sources produced by methods not according to the present invention to reach a lower limit of 32.7 weight percent is shown in Figures 2 and 3. The values ​​shown in Figures 2 and 3 are the average of measurements for three replicates of each combustible heat source.

[0424] The results in Figures 2 and 3 show that including a binder comprising polyvinyl alcohol in the formed combustible heat source and heating the formed combustible heat source to a temperature of at least 90 degrees Celsius for at least 45 minutes improves the chemical and physical stability of the combustible heat source made by the method of the present invention.

[0425] The results in Figures 2 and 3 indicate that including a binder comprising polyvinyl alcohol in a formed combustible heat source and heating the formed combustible heat source to a temperature of at least 90 degrees Celsius for at least 45 minutes advantageously significantly reduces the decomposition of the alkaline earth metal peroxide ignition aid as a result of exposure to environmental conditions. In particular, the results in Figures 2 and 3 indicate that including a binder comprising polyvinyl alcohol in a formed combustible heat source and heating the formed combustible heat source to a temperature of at least 90 degrees Celsius for at least 45 minutes advantageously significantly reduces the decomposition of the alkaline earth metal peroxide ignition aid as a result of exposure to high humidity.

[0426] The specific embodiments and examples described above illustrate but do not limit the invention, and it is understood that other embodiments of the invention may be made and that the specific embodiments and examples described herein are not exhaustive.

Claims

1. 1. A method for producing a combustible heat source for an aerosol-generating article, said method comprising: forming a combustible heat source comprising carbon, a binder, and an ignition aid, wherein the binder comprises polyvinyl alcohol and the ignition aid comprises an alkaline earth metal peroxide; and heating said formed combustible heat source to a temperature of at least 90 degrees Celsius for at least 45 minutes.

2. The method of claim 1 , wherein the combustible heat source comprises 15 to 65 weight percent of the alkaline earth metal peroxide ignition aid.

3. 3. The method of claim 1 or 2, wherein the ignition aid comprises calcium peroxide.

4. 4. The method of any one of claims 1 to 3, comprising heating the combustible heat source to a temperature of between 90 degrees Celsius and 150 degrees Celsius.

5. 5. The method of any one of claims 1 to 4, comprising heating the combustible heat source to a temperature of between 100 degrees Celsius and 140 degrees Celsius.

6. 6. The method of any one of claims 1 to 5, comprising heating the combustible heat source for 45 minutes to 24 hours.

7. 7. The method of any one of claims 1 to 6, comprising heating the combustible heat source for at least 90 minutes.

8. 8. The method of any one of claims 1 to 7, wherein the polyvinyl alcohol has a molecular weight of from 20,000 grams / mole to 200,000 grams / mole.

9. 9. The method of any one of claims 1 to 8, wherein the polyvinyl alcohol has a molecular weight of 125,000 grams per mole or less.

10. 10. The method of any one of claims 1 to 9, wherein the combustible heat source comprises at least 0.1 weight percent polyvinyl alcohol.

11. 11. The method of any one of claims 1 to 10, wherein the combustible heat source comprises 0.5 weight percent to 2 weight percent polyvinyl alcohol.

12. The method of any one of claims 1 to 11, wherein the binder further comprises carboxymethyl cellulose.

13. 13. The method of claim 12, wherein the combustible heat source comprises at least 2 weight percent carboxymethyl cellulose.

14. 14. The method of claim 12 or 13, wherein the ratio of weight percent carboxymethyl cellulose to weight percent polyvinyl alcohol in the combustible heat source is at least 2:1.

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