Solid aerosol-generating substrate and aerosol-generating article comprising a solid aerosol-generating substrate

Abstract

A solid aerosol-generating substrate for use in an aerosol-generating system, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid, wherein the solid aerosol-generating substrate is substantially tobacco-free, and wherein the solid aerosol-generating substrate is in the form of a sheet or a plurality of strands.

Description

[0001] SOLID AEROSOL-GENERATING SUBSTRATE AND AEROSOL-GENERATING ARTICLE COMPRISING A SOLID AEROSOL-GENERATING SUBSTRATE

[0002] The invention relates to a solid aerosol-generating substrate and to an aerosol-generating article comprising the solid aerosol-generating substrate. The invention also relates to an aerosolgenerating system comprising the aerosol-generating article and an electrically-operated aerosolgenerating device configured to heat the aerosol-generating article.

[0003] Aerosol-generating articles in which an aerosol-generating substrate, such as a nicotine- containing material, is heated in order to form an aerosol rather than combusted to form smoke, are known in the art. An aim of such ‘heated’ aerosol-generating articles is to reduce known harmful smoke constituents of the type produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes.

[0004] Typically in heated aerosol-generating articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate. In use, volatile compounds are released from the aerosol-generating substrate by heat transfer to the aerosolgenerating substrate from the heat source and entrained in air drawn through the aerosolgenerating article. As the released compounds cool, they condense to form an aerosol that is inhaled by the user.

[0005] A number of aerosol-generating systems comprising handheld aerosol-generating devices configured to heat aerosol-generating substrates of heated aerosol-generating articles are known in the art. These include electrically-operated aerosol-generating devices in which an aerosol is generated by the transfer of heat from one or more electrical heating elements of the aerosolgenerating device to the aerosol-generating substrate of the heated aerosol-generating article. Known handheld electrically operated aerosol-generating devices typically comprise a battery, control electronics and one or more electrical heating elements for heating the aerosol-generating substrate of a heated aerosol-generating article designed specifically for use with the aerosolgenerating device.

[0006] Some known electrically-operated aerosol-generating devices comprise an internal heating element that is configured to be inserted into the aerosol-generating substrate of a heated aerosol-generating article. For example, WO 2013 / 098410 A2 discloses an aerosol-generating system comprising an aerosol-generating article and an electrically-operated aerosol-generating device comprising a heating element in the form of a blade that is inserted into the aerosolgenerating substrate of the aerosol-generating article.

[0007] Other known electrically-operated aerosol-generating devices comprise one or more external heating elements. For example, WO 2020 / 1 15151 A1 discloses an aerosol-generating system comprising an aerosol-generating article and an electrically-operated aerosol-generating device comprising an external heating element that circumscribes the outer periphery of the aerosol-generating article.

[0008] Electrically-operated aerosol-generating devices comprising an inductor configured to inductively heat aerosol-generating substrates of heated aerosol-generating articles are also known in the art. For example, WO 2015 / 176898 A1 discloses an aerosol-generating system comprising an aerosol-generating article comprising an elongate susceptor in thermal contact with the aerosol-generating substrate and an electrically-operated aerosol-generating device having an inductor for heating the aerosol-generating substrate. In use, the fluctuating or alternating electromagnetic field produced by the inductor induces eddy currents in the susceptor, causing the susceptor to heat up as a result of one or both of resistive losses (Joule heating) and, where the susceptor is magnetic, hysteresis losses. Heat generated in the susceptor is transferred to the aerosol-generating substrate by conduction.

[0009] Aerosol-generating substrates for use in heated aerosol-generating articles typically comprise one or more aerosol formers, such as glycerine and propylene glycol.

[0010] In aerosol-generating systems for delivering nicotine to a user, pulmonary delivery of the inhalable aerosol generated from the nicotine-containing aerosol-generating substrate is important for user palatability and satisfaction. Nicotine adsorption through the pulmonary alveoli is rapid and efficient. By contrast, nicotine adsorption in the upper airways is slower and less efficient. Nicotine adsorption in the upper airways may also undesirably be perceived by a user as having a sensorial harshness and induce mouth and throat irritation.

[0011] To reduce perceived sensorial harshness and mouth and throat irritation and increase pulmonary delivery, it is known to include volatile acids in liquid nicotine-containing aerosolgenerating substrates. Without wishing to be bound by theory, interaction between volatile acids and nicotine in inhalable aerosols generated by heating such liquid nicotine-containing aerosolgenerating substrates results in at least the majority of the nicotine in the aerosol being protonated. Unlike unprotonated nicotine, protonated nicotine exists in the liquid phase or particulate phase of the aerosol, rather than in the gas phase of the aerosol. Reducing the level of nicotine in the gas phase of the aerosol, advantageously reduces perceived sensorial harshness of the aerosol and mouth and throat irritation. Reducing the level of nicotine in the gas phase of the aerosol, may also advantageously improve nicotine delivery to a user.

[0012] Liquid nicotine-containing aerosol-generating substrates are typically manufactured by simply mixing together components thereof at ambient temperature. Once produced, liquid nicotine-containing aerosol-generating substrates are typically sealed in a cartridge or other container prior to use.

[0013] Solid nicotine-containing aerosol-generating substrates are typically manufactured by methods that comprise not only mixing together components thereof but also one or more additional steps such as, for example, casting, drying, spraying, and crimping, at least some of which may be conducted at elevated temperature. As a result, acids having a high volatility may be more prone to being lost during manufacture and processing of solid nicotine-containing aerosol-generating substrates than liquid nicotine-containing aerosol-generating substrates. Consequently, inclusion of acids having a high volatility in solid nicotine-containing aerosolgenerating substrates may not be effective in reducing perceived sensorial harshness and mouth and throat irritation and increasing pulmonary delivery.

[0014] Acids having a low volatility are less prone to being lost during manufacture and processing of solid nicotine-containing aerosol-generating substrates than acids having a high volatility. However, acids having a low volatility are less readily released into inhalable aerosols generated by heating solid nicotine-containing aerosol-generating substrates than acids having a high volatility. Consequently, inclusion of acids having a low volatility in solid nicotine-containing aerosol-generating substrates may not be effective in reducing perceived sensorial harshness and mouth and throat irritation and increasing pulmonary delivery.

[0015] It would be desirable to provide a solid nicotine-containing aerosol-generating substrate that is capable upon heating of generating an inhalable aerosol that exhibits reduced perceived sensorial harshness and mouth and throat irritation compared to known solid nicotine-containing aerosol-generating substrates.

[0016] It would be desirable to provide a solid nicotine-containing aerosol-generating substrate that is capable upon heating of generating an inhalable aerosol that provides improved nicotine delivery to a user compared to known solid nicotine-containing aerosol-generating substrates.

[0017] The invention relates to a solid aerosol-generating substrate for use in an aerosolgenerating system. The solid aerosol-generating substrate may comprise nicotine. The solid aerosol-generating substrate may comprise one or more aerosol formers. The solid aerosolgenerating substrate may comprise one or more carboxylic acids. The one or more carboxylic acids may comprise at least one geminal dicarboxylic acid.

[0018] The invention also relates to an aerosol-generating article for use in an aerosol-generating system. The aerosol-generating article may comprise a solid aerosol-generating substrate. The solid aerosol-generating substrate may comprise nicotine. The solid aerosol-generating substrate may comprise one or more aerosol formers. The solid aerosol-generating substrate may comprise one or more carboxylic acids. The one or more carboxylic acids may comprise at least one geminal dicarboxylic acid.

[0019] The invention also relates to an aerosol-generating system. The aerosol-generating system may comprise an aerosol-generating article. The aerosol-generating article may comprise a solid aerosol-generating substrate. The solid aerosol-generating substrate may comprise nicotine. The solid aerosol-generating substrate may comprise one or more aerosol formers. The solid aerosol-generating substrate may comprise one or more carboxylic acids. The one or more carboxylic acids may comprise at least one geminal dicarboxylic acid. The aerosol-generating system may comprise an aerosol-generating device. The aerosol-generating device may be configured to heat the solid aerosol-generating substrate of the aerosol-generating article.

[0020] According to a first aspect of the invention there is provided a solid aerosol-generating substrate for use in an aerosol-generating system, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0021] According to the first aspect of the invention there is also provided a solid aerosolgenerating substrate for use in an aerosol-generating system, the solid aerosol-generating substrate comprising: tobacco material; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0022] According to a second aspect of the invention there is provided an aerosol-generating article for use in an aerosol-generating system, the aerosol-generating article comprising a solid aerosol-generating substrate, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0023] According to the second aspect of the invention there is also provided an aerosolgenerating article for use in an aerosol-generating system, the aerosol-generating article comprising a solid aerosol-generating substrate, the solid aerosol-generating substrate comprising: tobacco material; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0024] According to a third aspect of the invention there is provided an aerosol-generating system comprising: an aerosol-generating article comprising a solid aerosol-generating substrate, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid; and an aerosol-generating device configured to heat the solid aerosolgenerating substrate of the aerosol-generating article.

[0025] According to a third aspect of the invention there is also provided an aerosol-generating system comprising: an aerosol-generating article comprising a solid aerosol-generating substrate, the solid aerosol-generating substrate comprising: tobacco material; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid; and an aerosol-generating device configured to heat the solid aerosolgenerating substrate of the aerosol-generating article. As used herein, the term “aerosol-generating substrate” is used to describe a substrate comprising aerosol-generating material that is capable of releasing upon heating volatile compounds that can generate an aerosol.

[0026] As used herein, the term “aerosol” is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles, or liquid droplets, or a combination of solid particles and liquid droplets.

[0027] As used herein, the term “solid” is used to describe an aerosol-generating substrate that is not a liquid or a gas at 23°C. As used herein, the term “solid” is used to describe an aerosolgenerating substrate that has a stable size and shape and does not flow at 23°C.

[0028] As used herein, the term “nicotine” is used to describe nicotine, a nicotine base or a nicotine salt.

[0029] In embodiments in which the solid aerosol-generating substrate comprises a nicotine base or a nicotine salt, amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0030] As used herein, the term “aerosol former” is used to describe a compound that, in use, facilitates formation of the aerosol, and that preferably is substantially resistant to thermal degradation at the operating temperature of an aerosol-generating article or aerosol-generating system comprising the solid aerosol-generating substrate.

[0031] As used herein, the term “geminal dicarboxylic acid” is used to describe a carboxylic acid comprising two carboxyl groups attached to the same carbon atom. That is, a carboxylic acid comprising two COOH groups attached to the same carbon atom. A geminal dicarboxylic acid may also be referred to as a gem-dicarboxylic acid.

[0032] As used herein, the term “non-geminal dicarboxylic acid” is used to describe a carboxylic acid comprising two carboxyl groups attached to two different carbon atoms. That is, a carboxylic acid comprising two COOH groups attached to two different carbon atoms.

[0033] Unless stated otherwise, percentages by weight of components of the solid aerosolgenerating substrate recited herein are based on the total dry weight of the solid aerosolgenerating substrate.

[0034] As used herein, the term “aerosol-generating article” is used to describe an article comprising an aerosol-generating substrate that is heated to generate an inhalable aerosol for delivery to a user.

[0035] The aerosol-generating article has a proximal end through which, in use, an aerosol exits the aerosol-generating article for delivery to a user. The proximal end of the aerosol-generating article may also be referred to as the mouth end of the aerosol-generating article. In use, a user draws on the proximal end of the aerosol-generating article in order to inhale an aerosol generated by the aerosol-generating article.

[0036] The aerosol-generating article has a distal end. The distal end is opposite the proximal end.

[0037] Components of the aerosol-generating article may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article.

[0038] As used herein, the term “longitudinal” is used to describe the direction between the proximal end and the distal end of the aerosol-generating article.

[0039] As used herein, the term “transverse” is used to describe the direction perpendicular to the longitudinal direction. That is, the direction perpendicular to the direction between the proximal end and the distal end of the aerosol-generating article.

[0040] As used herein, the term “length” is used to describe the maximum dimension of the aerosol-generating article and components of the aerosol-generating article in the longitudinal direction. That is, the maximum dimension of the aerosol-generating article and components of the aerosol-generating article in the direction between the proximal end and the distal end of the aerosol-generating article.

[0041] As used herein, the term “width” is used to describe the maximum dimension of the aerosol-generating article and components of the aerosol-generating article in the transverse direction. That is, the maximum dimension of the aerosol-generating article and components of the aerosol-generating article in the direction perpendicular to the direction between the proximal end and the distal end of the aerosol-generating article.

[0042] As used herein, the term “aerosol-generating device” is used to describe a device that interacts with an aerosol generating substrate of an aerosol generating article to generate an aerosol. In particular, the term “aerosol-generating device” is used to describe a device that heats an aerosol generating substrate of an aerosol generating article to generate an aerosol.

[0043] Solid aerosol-generating substrates according to the first aspect of the invention comprise one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0044] Geminal dicarboxylic acids undergo thermal carboxylation to produce monocarboxylic acids. For example, malonic acid undergoes thermal decarboxylation to produce acetic acid:

[0045] A

[0046] CH2(COOH)2- CH3COOH + CO2

[0047] Inclusion of at least one geminal dicarboxylic acid in solid aerosol-generating substrates according to the first aspect of the invention may advantageously enable generation of an inhalable aerosol that exhibits reduced perceived sensorial harshness and mouth and throat irritation compared to known solid nicotine-containing aerosol-generating substrates.

[0048] Inclusion of at least one geminal dicarboxylic acid in solid aerosol-generating substrates according to the first aspect of the invention may advantageously enable generation of an inhalable aerosol that provides improved nicotine delivery to a user compared to known solid nicotine-containing aerosol-generating substrates.

[0049] The at least one geminal dicarboxylic acid may advantageously have a sufficiently low volatility that loss of the at least one geminal dicarboxylic acid during manufacturing and processing of the solid aerosol-generating substrate is substantially avoided.

[0050] Upon heating of the solid aerosol-generating substrate to generate an inhalable aerosol, the at least one geminal dicarboxylic acid may undergo thermal decarboxylation to produce a monocarboxylic acid. The monocarboxylic acid produced by decarboxylation of the at least one geminal dicarboxylic acid may advantageously have a sufficiently high volatility that the monocarboxylic acid is readily released into the inhalable aerosol generated upon heating of the solid aerosol-generating substrate. Interaction between the monocarboxylic acid produced by decarboxylation of the at least one geminal dicarboxylic acid and nicotine in the inhalable aerosol may advantageously increase the level of protonated nicotine in the liquid phase or particulate phase of the inhalable aerosol and reduce the level of unprotonated nicotine in the gas phase of the inhalable aerosol. This may advantageously reduce perceived sensorial harshness of the aerosol and mouth and throat irritation. This may also advantageously improve nicotine delivery to a user.

[0051] The solid aerosol-generating substrate may be in the form of a sheet.

[0052] As used herein, the term “sheet” describes a laminar element having a width and length substantially greater than the thickness thereof. The term “sheet” should be considered to encompass films and other laminar elements having a similar form.

[0053] The sheet may be gathered to form an aerosol-generating rod for inclusion in an aerosolgenerating article according to the second aspect of the invention.

[0054] The sheet may be gathered and wrapped to form an aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention.

[0055] As used herein, the term “gathered” is used to describe a sheet that is convoluted, folded, or otherwise compressed or constricted substantially transversely to the longitudinal axis of the aerosol-generating article.

[0056] The sheet may be textured. This may facilitate gathering of the sheet to form an aerosolgenerating rod for inclusion in an aerosol-generating article according to the second aspect of the invention.

[0057] As used herein, the term “textured” is used to describe a sheet that has been crimped, embossed, debossed, perforated or otherwise deformed. Textured sheets may comprise a plurality of spaced-apart indentations, protrusions, perforations or a combination thereof.

[0058] The sheet may be crimped.

[0059] As used herein, the term “crimped” is used to describe a sheet having a plurality of substantially parallel ridges or corrugations.

[0060] The crimped sheet may have a plurality of ridges or corrugations substantially parallel to the cylindrical axis of the aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention. This may advantageously facilitate gathering of the crimped sheet to form the aerosol-generating rod.

[0061] The sheet may be textured using suitable known machinery for texturing filter tow, paper and other materials.

[0062] The solid aerosol-generating substrate may be in the form of a hollow tubular element.

[0063] The hollow tubular element may be formed from a sheet, for example by rolling, or by other methods.

[0064] The solid aerosol-generating substrate may be in the form of a plurality of strands.

[0065] As used herein, the term “strand” is used to describe an elongate element having a length that is substantially greater than the width and thickness thereof. The term “strand” should be considered to encompass strips, shreds and other elongate elements having a similar form. The strands may be formed from a sheet, for example by cutting or shredding, or by other methods, for example, by an extrusion method.

[0066] The plurality of strands may be wrapped to form an aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention.

[0067] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of less than or equal to 300 degrees Celsius.

[0068] More advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of greater than or equal to 220 degrees Celsius.

[0069] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of greater than or equal to 100 degrees Celsius.

[0070] More advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of greater than or equal to 120 degrees Celsius.

[0071] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid at a temperature of between 100 degrees Celsius and 300 degrees Celsius, or between 100 degrees Celsius and 220 degrees Celsius.

[0072] More advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid at a temperature of between 120 degrees Celsius and 300 degrees Celsius, or between 120 degrees Celsius and 220 degrees Celsius.

[0073] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of less than or equal to 300 degrees Celsius.

[0074] More advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of less than or equal to 200 degrees Celsius.

[0075] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of greater than or equal to 100 degrees Celsius.

[0076] Advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of between 100 degrees Celsius and 300 degrees Celsius.

[0077] More advantageously, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of between 200 degrees Celsius and 300 degrees Celsius.

[0078] The one or more carboxylic acids may comprise at least one geminal dicarboxylic acid selected from malonic acid and derivatives thereof.

[0079] Preferably, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid selected from benzylmalonic acid, cyclobutane-1 ,1 -dicarboxylic acid, cyclohexane- 1 ,1- dicarboxylic acid, isopropylmalonic acid, malonic acid, methylmalonic acid, and phenylmalonic acid. Table 1 lists the monocarboxylic acids produced by thermal decarboxylation of benzylmalonic acid, cyclobutane-1 ,1 -dicarboxylic acid, cyclohexane- 1 ,1 -dicarboxylic acid, isopropylmalonic acid, malonic acid, methylmalonic acid, and phenylmalonic acid.

[0080] More preferably, the one or more carboxylic acids comprise at least one geminal dicarboxylic acid selected from malonic acid, benzylmalonic acid, isopropylmalonic acid, methylmalonic acid, and phenylmalonic acid.

[0081] Most preferably, the one or more carboxylic acids comprise malonic acid.

[0082] Table 1

[0083] The solid aerosol-generating substrate may comprise a single carboxylic acid, wherein the single carboxylic acid is a geminal dicarboxylic acid. In such embodiments, a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is 1 .

[0084] As used herein, the term “total carboxylic acid content” is used to describe the combined content of all carboxylic acids in the solid aerosol-generating substrate.

[0085] The solid aerosol-generating substrate may comprise a plurality of carboxylic acids, wherein the plurality of carboxylic acids comprise at least one geminal dicarboxylic acid. That is, the solid aerosol-generating substrate may comprise two or more carboxylic acids, wherein the two or more carboxylic acids comprise at least one geminal dicarboxylic acid. For example, the solid aerosol-generating substrate may comprise two carboxylic acids, three carboxylic acids, or four carboxylic acids.

[0086] The plurality of carboxylic acids may comprise a single geminal dicarboxylic acid.

[0087] The plurality of carboxylic acids may comprise a plurality of geminal dicarboxylic acids. That is, the plurality of carboxylic acids may comprise two or more geminal dicarboxylic acids. For example, the plurality of carboxylic acids may comprise two geminal dicarboxylic acids, three geminal dicarboxylic acids, or four geminal dicarboxylic acids. All of the plurality of carboxylic acids may be geminal dicarboxylic acids. In such embodiments, a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosolgenerating substrate to the weight percent total carboxylic acid content of the solid aerosolgenerating substrate is 1 .

[0088] The plurality of carboxylic acids may comprise at least one carboxylic acid that is not a geminal dicarboxylic acid. In such embodiments, a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is less than 1 .

[0089] The plurality of carboxylic acids may comprise at least one monocarboxylic acid. For example, the plurality of carboxylic acids may comprise at least one monocarboxylic acid selected from benzoic acid, lactic acid, and levulinic acid.

[0090] The plurality of carboxylic acids may comprise at least non-geminal dicarboxylic acid. For example, the plurality of carboxylic acids may comprise at least one non-geminal dicarboxylic acid selected from fumaric acid and succinic acid.

[0091] Advantageously, a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate may be greater than or equal to 0.15, greater than or equal to 0.3, greater than or equal to 0.5, greater than or equal to 0.6, or greater than or equal to 0.7.

[0092] More advantageously, a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate may be greater than or equal to 0.8, greater than or equal to 0.85, or greater than or equal to 0.9.

[0093] A ratio of the weight percent geminal dicarboxylic acid content of the solid aerosolgenerating substrate to the weight percent total carboxylic acid content of the solid aerosolgenerating substrate may be between 0.15 and 1 , between 0.3 and 1 , between 0.5 and 1 , between 0.6 and 1 , between 0.7 and 1 , between 0.8 and 1 , between 0.85 and 1 , or between 0.9 and 1.

[0094] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of greater than or equal to 0.4 percent by weight, greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, greater than or equal to 1.5 percent by weight, or greater than or equal to 2 percent by weight.

[0095] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content content of less than or equal to 1 percent by weight, less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight.

[0096] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of between 0.4 percent by weight and 12 percent by weight, between 0.4 percent by weight and 8 percent by weight, between 0.4 percent by weight and 6 percent by weight, or between 0.4 percent by weight and 4 percent by weight.

[0097] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of between 0.5 percent by weight and 1 percent by weight, between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

[0098] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of between 1 percent by weight and 12 percent by weight, between 1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight.

[0099] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of between 1.5 percent by weight and 12 percent by weight, between 1.5 percent by weight and 8 percent by weight, between 1 .5 percent by weight and 6 percent by weight, or between 1 .5 percent by weight and 4 percent by weight.

[0100] The solid aerosol-generating substrate may have a geminal dicarboxylic acid content of between 2 percent by weight and 12 percent by weight, between 2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

[0101] The solid aerosol-generating substrate may have a total carboxylic acid content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, greater than or equal to 1 .5 percent by weight, or greater than or equal to 2 percent by weight.

[0102] The solid aerosol-generating substrate may have a total carboxylic acid content of less than or equal to 15 percent by weight, less than or equal to 8 percent by weight, less than or equal to 6 percent by weight, or less than or equal to 4 percent by weight.

[0103] The solid aerosol-generating substrate may have a total carboxylic acid content of between 0.5 percent by weight and 15 percent by weight, between 0.5 percent by weight and 8 percent by weight, between 0.5 percent by weight and 6 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

[0104] The solid aerosol-generating substrate may have a total carboxylic acid content of between 1 percent by weight and 15 percent by weight, between 1 percent by weight and 8 percent by weight, between 1 percent by weight and 6 percent by weight, or between 1 percent by weight and 4 percent by weight.

[0105] The solid aerosol-generating substrate may have a total carboxylic acid content of between 1.5 percent by weight and 15 percent by weight, between 1.5 percent by weight and 8 percent by weight, between 1 .5 percent by weight and 6 percent by weight, or between 1 .5 percent by weight and 4 percent by weight. The solid aerosol-generating substrate may have a total carboxylic acid content of between 2 percent by weight and 15 percent by weight, between 2 percent by weight and 8 percent by weight, between 2 percent by weight and 6 percent by weight, or between 2 percent by weight and 4 percent by weight.

[0106] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 1 , or greater than or equal to 2.

[0107] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be less than or equal to 7, less than or equal to 5, less than or equal to 4, or less than or equal to 3.

[0108] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be between 0.25 and 7, between 0.25 and 5, between 0.25 and 4, or between 0.25 and 3.

[0109] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be between 0.5 and 7, between 0.5 and 5, between 0.5 and 4, or between 0.5 and 3.

[0110] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be between 1 and 7, between 1 and 5, between 1 and 4, or between 1 and 3.

[0111] A molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosol-generating substrate may be between 2 and 7, between 2 and 5, between 2 and 4, or between 2 and 3.

[0112] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be greater than or equal to 0.5, greater than or equal to 1 , greater than or equal to 1 .5, or greater than or equal to 2.

[0113] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be less than or equal to 7, less than or equal to 5, less than or equal to 4, or less than or equal to 3.

[0114] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 0.5 and 7, between 0.5 and 5, between 0.5 and 4, or between 0.5 and 3.

[0115] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 1 and 7, between 1 and 5, between 1 and 4, or between 1 and 3.

[0116] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 1 .5 and 7, between 1 .5 and 5, between 1 .5 and 4, or between 1 .5 and 3.

[0117] A molar ratio of total carboxylic acid to nicotine in the solid aerosol-generating substrate may be between 2 and 7, between 2 and 5, between 2 and 4, or between 2 and 3.

[0118] The at least one geminal carboxylic acid may be substantially evenly distributed within the solid aerosol-generating substrate. The at least one geminal carboxylic acid may be unevenly distributed within the solid aerosol-generating substrate.

[0119] In particular, a majority of the at least one geminal carboxylic acid may be located proximate an outer surface of the solid aerosol-generating substrate.

[0120] The solid aerosol-generating substrate comprises one or more aerosol-formers.

[0121] Examples of suitable aerosol formers include: polyhydric alcohols, such as 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol; 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 dimethyl tetradecanedioate.

[0122] Preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols.

[0123] More preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols selected from 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol.

[0124] Most preferably, the solid aerosol-generating substrate comprises one or more polyhydric alcohols selected from glycerine and propylene glycol. The solid aerosol-generating substrate may comprise glycerine. The solid aerosol-generating substrate may comprise propylene glycol. The aerosol former may comprise a combination of glycerine and propylene glycol.

[0125] The solid aerosol-generating substrate may have a total aerosol former content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0126] As used herein, the term “total aerosol former content” is used to describe the combined content of all aerosol formers in the solid aerosol-generating substrate.

[0127] In certain embodiments, the solid aerosol-generating substrate may have a total aerosol former content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0128] In such embodiments, solid aerosol-generating substrate may have a total aerosol former content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

[0129] The solid aerosol-generating substrate may have a total aerosol former content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

[0130] The solid aerosol-generating substrate may have a total aerosol former content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight. The solid aerosol-generating substrate may have a total aerosol former content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

[0131] Solid aerosol-generating substrates having a total aerosol former content of between 5 percent by weight and 30 percent by weight are described as having a relatively low total aerosol former content.

[0132] In other embodiments, the solid aerosol-generating substrate may have a total aerosol former content of greater than or equal to 40 percent by weight, greater than or equal to 45 percent by weight, or greater than or equal to 50 percent by weight.

[0133] In such embodiments, solid aerosol-generating substrate may have a total aerosol former content of less than or equal to 80 percent by weight, less than or equal to 75 percent by weight, or less than or equal to 70 percent by weight.

[0134] The solid aerosol-generating substrate may have a total aerosol former content of between 40 percent by weight and 80 percent by weight, between 40 percent by weight and 75 percent by weight, or between 40 percent by weight and 70 percent by weight.

[0135] The solid aerosol-generating substrate may have a total aerosol former content of between 45 percent by weight and 80 percent by weight, between 45 percent by weight and 75 percent by weight, or between 45 percent by weight and 70 percent by weight.

[0136] The solid aerosol-generating substrate may have a total aerosol former content of between 50 percent by weight and 80 percent by weight, between 50 percent by weight and 75 percent by weight, or between 50 percent by weight and 70 percent by weight.

[0137] Solid aerosol-generating substrates having a total aerosol former content of between 40 percent by weight and 80 percent by weight are described as having a relatively high total aerosol former content.

[0138] The solid aerosol-generating substrate comprises nicotine.

[0139] The solid aerosol-generating substrate may have a nicotine content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, or greater than or equal to 1 .5 percent by weight.

[0140] The solid aerosol-generating substrate may have a nicotine content of less than or equal to 10 percent by weight. The solid aerosol-generating substrate may have a nicotine content of less than or equal to 5 percent by weight, less than or equal to 4 percent by weight, or less than or equal to 3 percent by weight.

[0141] The solid aerosol-generating substrate may have a nicotine content of between 0.5 percent by weight and 10 percent by weight. For example, the solid aerosol-generating substrate may have a nicotine content of between 0.5 percent by weight and 5 percent by weight, between 0.5 percent by weight and 4 percent by weight or between 0.5 percent by weight and 3 percent by weight.

[0142] The solid aerosol-generating substrate may have a nicotine content of between 1 percent by weight and 10 percent by weight. For example, the solid aerosol-generating substrate may have a nicotine content of between 1 percent by weight and 5 percent by weight, between 1 percent by weight and 4 percent by weight or between 1 percent by weight and 3 percent by weight.

[0143] The solid aerosol-generating substrate may have a nicotine content of between 1.5 percent by weight and 10 percent by weight. For example, the solid aerosol-generating substrate may have a nicotine content of between 1 .5 percent by weight and 5 percent by weight, between 1 .5 percent by weight and 4 percent by weight or between 1 .5 percent by weight and 3 percent by weight.

[0144] The solid aerosol-generating substrate may comprise natural nicotine.

[0145] The solid aerosol-generating substrate may comprise synthetic nicotine.

[0146] The solid aerosol-generating substrate may comprise a combination of natural nicotine and synthetic nicotine.

[0147] The solid aerosol-generating substrate may comprise tobacco material.

[0148] As used herein, the term “tobacco material” is used to describe any material comprising tobacco, including, but not limited to, tobacco leaf, tobacco rib, tobacco stem, tobacco stalk, tobacco dust, expanded tobacco, reconstituted tobacco material and homogenised tobacco material.

[0149] The tobacco material may, for example, be in the form of powder, granules, pellets, strands, sheets or any combination thereof.

[0150] Where the solid aerosol-generating substrate comprises tobacco material, the solid aerosol-generating substrate comprises endogenous nicotine.

[0151] As used herein, the term “endogenous nicotine” is used to describe nicotine intrinsic to tobacco material in the solid aerosol-generating substrate.

[0152] The solid aerosol-generating substrate may also comprise exogenous nicotine.

[0153] As used herein, the term “exogenous nicotine” is used to describe nicotine in the solid aerosol-generating substrate that is extrinsic to tobacco material in the solid aerosol-generating substrate.

[0154] The solid aerosol-generating substrate may comprise cut filler.

[0155] As used herein, the term “cut filler” is used to describe a blend of shredded tobacco plant material, including, in particular, one or more of tobacco leaf lamina, tobacco stems, and tobacco ribs. Preferably, the cut filler comprises at least 25 percent of tobacco leaf lamina, more preferably at least 50 percent of tobacco leaf lamina, still more preferably at least 75 percent of tobacco leaf lamina, and most preferably at least 90 percent of tobacco leaf lamina.

[0156] The cut filler may resemble cut filler used for conventional smoking articles, such as cigarettes.

[0157] The cut width of the cut filler may be between 0.3 millimetres and 2.0 millimetres, between 0.5 millimetres and 1.2 millimetres, or between 0.6 millimetres and 0.9 millimetres.

[0158] Preferably, the strand length of the cut filler is between 10 millimetres and 40 millimetres.

[0159] Advantageously, the weight of the cut filler is between 25 milligrams and 150 milligrams, preferably between 30 milligrams and 125 milligrams, more preferably between 40 milligrams and 100 milligrams. This amount of cut filler typically allows for sufficient material for the formation of an aerosol during early puffs.

[0160] Preferably, the aerosol former content of the cut filler is within the ranges recited above for solid aerosol-generating substrates described as having a relatively low total aerosol former content.

[0161] Preferably, the cut filler is soaked with the one or more aerosol formers. Soaking the cut filler with the one or more aerosol formers may be done by spraying or by other suitable application methods. The one or more aerosol formers may be applied to the blend during preparation of the cut filler. For example, the one or more aerosol formers may be applied to the blend in a direct conditioning casing cylinder (DCCC). Conventional machinery can be used for applying one or more aerosol formers to the cut filler.

[0162] Preferably, the cut filler is soaked with the one or more carboxylic acids. Soaking the cut filler with the one or more carboxylic acids may be done by spraying or by other suitable application methods. The one or more carboxylic acids may be applied to the blend during preparation of the cut filler. For example, the one or more carboxylic acids may be applied to the blend in a direct conditioning casing cylinder (DCCC). Conventional machinery may be used for applying the one or more carboxylic acids to the cut filler.

[0163] The aerosol-generating substrate may comprise homogenised tobacco material.

[0164] As used herein, the term “homogenised tobacco material” is used to describe a material formed by agglomerating particulate tobacco.

[0165] Preferably, the aerosol former content of the homogenised tobacco material is within the ranges recited above for solid aerosol-generating substrates described as having a relatively low total aerosol former content.

[0166] The homogenised plant material may be formed by any suitable method. For example, the homogenous tobacco material may be produced by casting, extrusion, or paper making processes. The at least one-geminal carboxylic acid may be mixed with other components of the homogenised plant material prior to casting or extrusion. This may result in the at least one- geminal carboxylic acid being substantially evenly distributed within the solid aerosol-generating substrate.

[0167] The at least one geminal carboxylic acid may be applied to the homogenised plant material after casting or extrusion by spraying, injection or by other suitable application methods. This may result in the at least one geminal carboxylic acid being unevenly distributed within the solid aerosol-generating substrate. For example, where the at least one geminal carboxylic acid is sprayed onto the homogenised plant material after casting or extrusion, a majority of the at least one geminal carboxylic acid may be located proximate an outer surface of the solid aerosolgenerating substrate.

[0168] The sheet of homogenised plant material may be gathered.

[0169] The sheet of homogenised plant material may be textured.

[0170] The sheet of homogenised plant material may be crimped.

[0171] The sheet of homogenised plant material may be cut or otherwise divided into a plurality of strands.

[0172] The solid aerosol-generating substrate may be substantially tobacco-free.

[0173] As used herein, the term “substantially tobacco-free” is used to describe a solid aerosolgenerating substrate having a tobacco content of less than 1 percent by weight. For example, the solid aerosol-generating substrate may have a tobacco content of less than 0.75 percent by weight, less than 0.5 percent by weight, or less than 0.25 percent by weight.

[0174] The solid aerosol-generating substrate may be tobacco-free.

[0175] As used herein, the term “tobacco-free” is used to describe a solid aerosol-generating substrate having a tobacco content of 0 percent by weight.

[0176] The solid aerosol-generating substrate may comprise one or more cellulose based agents.

[0177] As used herein, the term “cellulose based agent” is used to describe a cellulosic substance. Examples of cellulose based agents include cellulose based binding agents, cellulose based film-forming agents, and cellulose based strengthening agents.

[0178] The solid aerosol-generating substrate may comprise a plurality of cellulose based agents. That is, the solid aerosol-generating substrate may comprise two or more cellulose based agents. For example, the solid aerosol-generating substrate may comprise two cellulose based agents, three cellulose based agents, four cellulose based agents, or five cellulose based agents.

[0179] The solid aerosol-generating substrate may have a total cellulose based agent content of greater than or equal to 25 percent by weight, greater than or equal to 30 percent by weight, or greater than or equal to 35 percent by weight. As used herein, the term “total cellulose based agent” is used to describe the combined content of all cellulose based agents in the solid aerosol-generating substrate.

[0180] The solid aerosol-generating substrate may have a total cellulose based agent content of less than or equal to 55 percent by weight, less than or equal to 50 percent by weight, or less than or equal to 45 percent by weight.

[0181] The solid aerosol-generating substrate may have a total cellulose based agent content of between 25 percent by weight and 55 percent by weight, between 25 percent by weight and 50 percent by weight, or between 25 percent by weight and 45 percent by weight.

[0182] The solid aerosol-generating substrate may have a total cellulose based agent content of between 30 percent by weight and 55 percent by weight, between 30 percent by weight and 50 percent by weight, or between 30 percent by weight and 45 percent by weight.

[0183] The solid aerosol-generating substrate may have a total cellulose based agent content of between 35 percent by weight and 55 percent by weight, between 35 percent by weight and 50 percent by weight, or between 35 percent by weight and 45 percent by weight.

[0184] The solid aerosol-generating substrate may comprise one or more cellulose based filmforming agents.

[0185] As used herein, the term “cellulose based film-forming agent” is used to describe a cellulosic polymer capable, by itself or in the presence of an auxiliary thickening agent, of forming a continuous film.

[0186] The solid aerosol-generating substrate may comprise one or more cellulose based binding agents.

[0187] The solid aerosol-generating substrate may comprise one or more cellulose based filmforming agents or cellulose based binding agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), hydroxyethyl cellulose (HEC), hydroxyethyl methylcellulose (HEMC), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and methylcellulose (MC).

[0188] The solid aerosol-generating substrate may comprise one or more cellulose based filmforming agents or cellulose binding agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC).

[0189] The solid aerosol-generating substrate may comprise one or more cellulose based filmforming agents or cellulose based binding agents selected from carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC).

[0190] The solid aerosol-generating substrate may be a solid aerosol-generating film comprising carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC).

[0191] The solid aerosol-generating substrate may be a solid aerosol-generating film comprising sodium carboxymethyl cellulose (Na-CMC) and hydroxypropyl methylcellulose (HPMC). The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of greater than or equal to 15 percent by weight, greater than or equal to 20 percent by weight, or greater than or equal to 25 percent by weight.

[0192] As used herein, the term “total cellulose based film-forming agent content” is used to describe the combined content of all cellulose based film-forming agents in the solid aerosolgenerating substrate.

[0193] The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of less than or equal to 40 percent by weight, less than or equal to 35 percent by weight, or less than or equal to 30 percent by weight.

[0194] The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 15 percent by weight and 40 percent by weight, between 15 percent by weight and 35 percent by weight, or between 15 percent by weight and 30 percent by weight.

[0195] The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 20 percent by weight and 40 percent by weight, between 20 percent by weight and 35 percent by weight, or between 20 percent by weight and 30 percent by weight.

[0196] The solid aerosol-generating substrate may have a total cellulose based film-forming agent content of between 25 percent by weight and 40 percent by weight, between 25 percent by weight and 35 percent by weight, or between 25 percent by weight and 30 percent by weight.

[0197] The solid aerosol-generating substrate may have a total cellulose based binding agent content of greater than or equal to 2 percent by weight, greater than or equal to 3 percent by weight, or greater than or equal to 4 percent by weight.

[0198] As used herein, the term “total cellulose based binding agent content” is used to describe the combined content of all cellulose based binding agents in the solid aerosol-generating substrate.

[0199] The solid aerosol-generating substrate may have a total cellulose based binding agent content of less than or equal to 10 percent by weight, less than or equal to 9 percent by weight, or less than or equal to 8 percent by weight.

[0200] The solid aerosol-generating substrate may have a total cellulose based binding agent content of between 2 percent by weight and 10 percent by weight, between 2 percent by weight and 9 percent by weight, or between 2 percent by weight and 8 percent by weight.

[0201] The solid aerosol-generating substrate may have a total cellulose based binding agent content of between 3 percent by weight and 10 percent by weight, between 3 percent by weight and 9 percent by weight, or between 3 percent by weight and 8 percent by weight.

[0202] The solid aerosol-generating substrate may have a total cellulose based binding agent content of between 4 percent by weight and 10 percent by weight, between 4 percent by weight and 9 percent by weight, or between 4 percent by weight and 8 percent by weight. The solid aerosol-generating substrate may comprise one or more cellulose based strengthening agents.

[0203] Inclusion of one or more cellulose based strengthening agents in the solid aerosolgenerating substrate may advantageously increase the tensile strength of the solid aerosolgenerating substrate. In particular, where the solid aerosol-generating substrate is a solid aerosol-generating film, inclusion of one or more cellulose based strengthening agents in the solid aerosol-generating substrate may advantageously increase the tensile strength of the solid aerosol-generating film. A solid aerosol-generating substrate having a higher tensile strength may advantageously be less likely to deteriorate or break during manufacture and storage.

[0204] The solid aerosol-generating substrate may comprise one or more cellulose based strengthening agents selected from cellulose fibres, cellulose powder, and microcrystalline cellulose (MCC).

[0205] The solid aerosol-generating substrate may comprise cellulose fibres. For example, the solid aerosol-generating substrate may be a solid aerosol-generating film comprising cellulose fibres. Cellulose fibres may be particularly effective at increasing the tensile strength of the solid aerosol-generating substrate.

[0206] The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0207] As used herein, the term “total cellulose based strengthening agent content” is used to describe the combined content of all cellulose based strengthening agents in the solid aerosolgenerating substrate.

[0208] The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

[0209] The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

[0210] The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

[0211] The solid aerosol-generating substrate may have a total cellulose based strengthening agent content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight. The solid aerosol-generating substrate may have a cellulose fibre content of greater than or equal to 5 percent by weight, or greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0212] The solid aerosol-generating substrate may have a cellulose fibre content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

[0213] The solid aerosol-generating substrate may have a cellulose fibre content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

[0214] The solid aerosol-generating substrate may have a cellulose fibre content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

[0215] The solid aerosol-generating substrate may have a cellulose fibre content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

[0216] The solid aerosol-generating substrate may have a microcrystalline cellulose content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0217] The solid aerosol-generating substrate may have a microcrystalline cellulose content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight.

[0218] The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

[0219] The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

[0220] The solid aerosol-generating substrate may have a microcrystalline cellulose content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

[0221] The solid aerosol-generating substrate may have a cellulose powder content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight.

[0222] The solid aerosol-generating substrate may have a cellulose powder content of less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight. The solid aerosol-generating substrate may have a cellulose powder content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight.

[0223] The solid aerosol-generating substrate may have a cellulose powder content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight.

[0224] The solid aerosol-generating substrate may have a cellulose powder content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 25 percent by weight, or between 15 percent by weight and 20 percent by weight.

[0225] The solid aerosol-generating substrate may comprise one or more non-cellulose based agents. As used herein, the term “non-cellulose based agent” is used to describe non-cellulose based binding agents, non-cellulose based gelling agents, and non-cellulose based thickening agents.

[0226] As used herein, the term “non-cellulose based gelling agent” is used to describe a non- cellulosic substance that, when added to an aqueous or non-aqueous liquid composition, increases the viscosity of the liquid composition through the formation of a colloidal gel.

[0227] Non-cellulose based gelling agents include, but are not limited to, hydrogen-bond crosslinking non-cellulose based gelling agents and ionic crosslinking non-cellulose based gelling agents.

[0228] As used herein, the term “hydrogen-bond crosslinking non-cellulose based gelling agent” is used to describe a non-cellulose based gelling agent that forms non-covalent crosslinking bonds or physical crosslinking bonds via hydrogen bonding.

[0229] As used herein, the term “ionic crosslinking non-cellulose based gelling agent” is used to describe a non-cellulose based gelling agent that forms non-covalent crosslinking bonds or physical crosslinking bonds via ionic bonding.

[0230] As used herein, the term “non-cellulose based thickening agent” is used to describe a non- cellulosic substance that, when added to an aqueous or non-aqueous liquid composition, increases the viscosity of the liquid composition without substantially modifying its other properties. The one or more non-cellulose based thickening agents may increase stability, and improve suspension of components in the liquid composition. A thickening agent may also be referred to as a “rheology modifying agent” or “viscosifying agent”.

[0231] The solid aerosol-generating substrate may comprise one or more non-cellulose based agents selected from agar, agarose alginates, gelatine, gellan gum, guar gum, gum arabic, iota carrageenan, kappa carrageenan, konjac gum, lambda carrageenan, locust bean gum, low acyl gellan, pectin, starch, and xanthan gum. The solid aerosol-generating substrate may have a total non-cellulose based agent content of greater than or equal to 1 percent by weight, greater than or equal to 2 percent by weight, or greater than or equal to 3 percent by weight.

[0232] As used herein, the term “total non-cellulose based agent content” is used to describe the combined content of all non-cellulose based agents in the solid aerosol-generating substrate.

[0233] The solid aerosol-generating substrate may have a total non-cellulose based agent content of less than or equal to 10 percent by weight, less than or equal to 8 percent by weight, or less than or equal to 6 percent by weight.

[0234] The solid aerosol-generating substrate may have a total non-cellulose based agent content of between 1 percent by weight and 10 percent by weight, between 1 percent by weight and 8 percent by weight, or between 1 percent by weight and 6 percent by weight.

[0235] The solid aerosol-generating substrate may have a total non-cellulose based agent content of between 2 percent by weight and 10 percent by weight, between 2 percent by weight and 8 percent by weight, or between 2 percent by weight and 6 percent by weight.

[0236] The solid aerosol-generating substrate may have a total non-cellulose based agent content of between 3 percent by weight and 10 percent by weight, between 3 percent by weight and 8 percent by weight, or between 3 percent by weight and 6 percent by weight.

[0237] The solid aerosol-generating substrate may be non-colloidal.

[0238] The solid aerosol-generating substrate may have a total non-cellulose based gelling agent content of less than 1 percent by weight. For example, the solid aerosol-generating substrate may have a total non-cellulose based gelling agent content of less than 0.75 percent by weight, less than 0.5 percent by weight, or less than 0.25 percent by weight.

[0239] The solid aerosol-generating substrate may have a total non-cellulose based gelling agent content of 0 percent by weight.

[0240] The solid aerosol-generating substrate may not comprise iota-carrageenan or kappa- carrageenan. Solid aerosol-generating substrates that do not comprise iota-carrageenan or kappa-carrageenan may advantageously remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius.

[0241] The solid aerosol-generating substrate may not comprise agar. Solid aerosol-generating substrates that do not agar may advantageously remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius.

[0242] The solid aerosol-generating substrate may comprise a plurality of thermally conductive carbon particles.

[0243] As used herein, the term “thermally conductive carbon particles” is used to describe particles consisting of one or more of graphite, expanded graphite, graphene, carbon nanotubes, charcoal, and diamond. The solid aerosol-generating substrate may have a total thermally conductive carbon particle content of greater than or equal to 10 percent by weight, greater than or equal to 20 percent by weight, or greater than or equal to 30 percent by weight.

[0244] As used herein, the term “total thermally conductive carbon particle content” is used to describe the combined content of all thermally conductive carbon particles in the solid aerosolgenerating substrate.

[0245] The solid aerosol-generating substrate may have a total thermally conductive carbon particle content of less than or equal to 90 percent by weight, less than or equal to 80 percent by weight, or less than or equal to 70 percent by weight.

[0246] The solid aerosol-generating substrate may have a total thermally conductive carbon particle content of between 10 percent by weight and 90 percent by weight, between 10 percent by weight and 80 percent by weight, or between 10 percent by weight and 70 percent by weight.

[0247] The solid aerosol-generating substrate may have a total thermally conductive carbon particle content of between 20 percent by weight and 90 percent by weight, between 20 percent by weight and 80 percent by weight, or between 20 percent by weight and 70 percent by weight.

[0248] The solid aerosol-generating substrate may have a total thermally conductive carbon particle content of between 30 percent by weight and 90 percent by weight, between 30 percent by weight and 80 percent by weight, or between 30 percent by weight and 70 percent by weight.

[0249] The solid aerosol-generating substrate may comprise one or more flavourants.

[0250] The solid aerosol-generating substrate may comprise any suitable flavourant or combination of flavourants. Suitable flavourants include, but are not limited to: menthol; peppermint oil; gamma octalactone; vanillin; ethyl vanillin; methyl salicylate; linalool; bergamot oil; geranium oil; ginger oil; and lemon oil.

[0251] As used herein, the term “menthol” is used to describe the compound 2-isopropyl-5- methylcyclohexanol in any of its isomeric forms.

[0252] The solid aerosol-generating substrate may comprise one or more natural flavourants.

[0253] The solid aerosol-generating substrate may comprise one or more synthetic flavourants.

[0254] The solid aerosol-generating substrate may comprise a combination of one or more natural flavourants and one or more synthetic flavourants.

[0255] The solid aerosol-generating substrate may have a total flavourant content of greater than or equal to 0.5 percent by weight, greater than or equal to 1 percent by weight, or greater than or equal to 2 percent by weight.

[0256] As used herein, the term “total flavourant content” is used to describe the combined content of all flavourants in the solid aerosol-generating substrate. The solid aerosol-generating substrate may have a total flavourant content of less than or equal to 6 percent by weight, less than or equal to 5 percent by weight, or less than or equal to 4 percent by weight.

[0257] The solid aerosol-generating substrate may have a total flavourant content of between 0.5 percent by weight and 6 percent by weight, between 0.5 percent by weight and 5 percent by weight, or between 0.5 percent by weight and 4 percent by weight.

[0258] The solid aerosol-generating substrate may have a total flavourant content of between

[0259] 1 percent by weight and 6 percent by weight, between 1 percent by weight and 5 percent by weight, or between 1 percent by weight and 4 percent by weight.

[0260] The solid aerosol-generating substrate may have a total flavourant content of between

[0261] 2 percent by weight and 6 percent by weight, between 2 percent by weight and 5 percent by weight, or between 2 percent by weight and 4 percent by weight.

[0262] The solid aerosol-generating substrate may comprise water.

[0263] The solid aerosol-generating substrate may have a water content of greater than or equal to 5 percent by weight, greater than or equal to 10 percent by weight, or greater than or equal to 15 percent by weight based on the total weight of the solid aerosol-generating substrate.

[0264] The solid aerosol-generating substrate may have a water content of less than or equal to less than or equal to 30 percent by weight, less than or equal to 25 percent by weight, or less than or equal to 20 percent by weight based on the total weight of the solid aerosol-generating substrate.

[0265] The solid aerosol-generating substrate may have a water content of between 5 percent by weight and 30 percent by weight, between 5 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight based on the total weight of the solid aerosol-generating substrate.

[0266] The solid aerosol-generating substrate may have a water content of between 10 percent by weight and 30 percent by weight, between 10 percent by weight and 25 percent by weight, or between 10 percent by weight and 20 percent by weight based on the total weight of the solid aerosol-generating substrate.

[0267] The solid aerosol-generating substrate may have a water content of between 15 percent by weight and 30 percent by weight, between 15 percent by weight and 20 percent by weight, or between 15 percent by weight and 20 percent by weight based on the total weight of the solid aerosol-generating substrate.

[0268] The solid aerosol-generating substrate may remain solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius. For example, the solid aerosol-generating substrate may remain solid when heated to a temperature of between 200 degrees Celsius and 320 degrees Celsius, between 220 degrees Celsius and 300 degrees Celsius, or between 240 degrees Celsius and 280 degrees Celsius.

[0269] The solid aerosol-generating substrate may be a solid aerosol-generating film.

[0270] Preferably, the solid aerosol-generating film is substantially tobacco-free.

[0271] More preferably, the solid aerosol-generating film is tobacco-free.

[0272] Preferably, the aerosol former content of the solid aerosol-generating film is within the ranges recited above for solid aerosol-generating substrates described as having a relatively high total aerosol former content.

[0273] The solid aerosol-generating film may be formed by any suitable method. For example, the solid aerosol-generating film may be formed by batch casting, continuous casting, or extrusion.

[0274] The at least one-geminal carboxylic acid may be mixed with other components of the solid aerosol-generating film prior to casting or extrusion. This may result in the at least one-geminal carboxylic acid being substantially evenly distributed within the solid aerosol-generating film.

[0275] The at least one geminal carboxylic acid may be applied to the film after casting or extrusion by spraying, injection or by other suitable application methods. This may result in the at least one geminal carboxylic acid being unevenly distributed within the solid aerosol-generating film. For example, where the at least one geminal carboxylic acid is sprayed onto the film after casting or extrusion, a majority of the at least one geminal carboxylic acid may be located proximate an outer surface of the solid aerosol-generating film.

[0276] The solid aerosol-generating film may be self-supporting. In other words, the properties of the solid aerosol-generating film may be such that, even if the solid aerosol-generating film is formed by casting a slurry onto a support surface, the solid aerosol-generating film can be separated from the support surface.

[0277] The solid aerosol-generating film may be disposed on a support or the solid aerosolgenerating film may be sandwiched between other materials. This may enhance the mechanical stability of the solid aerosol-generating film. For example, the solid aerosol-generating film may be disposed on a laminar support.

[0278] The solid aerosol-generating film may be gathered.

[0279] The solid aerosol-generating film may be textured.

[0280] The solid aerosol-generating film may be crimped.

[0281] The solid aerosol-generating film may be cut or otherwise divided into a plurality of strands.

[0282] The solid aerosol-generating film may be incorporated directly into an aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention. The solid aerosol-generating film may be applied to a laminar support before being incorporated into an aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention. For example, the solid aerosol-generating film may be applied to the surface of a sheet material. Suitable sheet materials for use as the laminar support include, but are not limited, to: paper; cardboard; and homogenised plant material. For example, the solid aerosol-generating film may be applied to a paper sheet, an aluminium coated paper sheet, or a polyethylene coated paper sheet.

[0283] The laminar support with the solid aerosol-generating film applied thereto may be cut or otherwise divided into a plurality of strands.

[0284] The laminar support with the solid aerosol-generating film applied thereto may be gathered.

[0285] The laminar support with the solid aerosol-generating film applied thereto may be textured.

[0286] The laminar support with the solid aerosol-generating film applied thereto may be crimped.

[0287] The solid aerosol-generating film may be applied to a tubular support before being incorporated into an aerosol-generating rod for inclusion in an aerosol-generating article according to the second aspect of the invention. For example, the solid aerosol-generating film may be applied to the inner surface of a hollow tubular support.

[0288] The solid aerosol-generating film may have a thickness of greater than or equal to 0.05 millimetres, greater than or equal to 0.1 millimetres, greater than or equal to 0.2 millimetres, or greater than or equal to 0.3 millimetres.

[0289] The solid aerosol-generating film may have a thickness of less than or equal to

[0290] 1 .2 millimetres, less than or equal to 1 millimetre, less than or equal to 0.8 millimetres, less than or equal to 0.6 millimetres, or less than or equal to 0.4 millimetres.

[0291] The solid aerosol-generating film may have a thickness of between 0.05 millimetres and

[0292] 1.2 millimetres, between 0.05 millimetres and 1 millimetre, between 0.05 millimetres and 0.8 millimetres, between 0.05 millimetres and 0.6 millimetres, or between 0.05 millimetres and 0.4 millimetres.

[0293] The solid aerosol-generating film may have a thickness of between 0.1 millimetres and

[0294] 1.2 millimetres, between 0.1 millimetres and 1 millimetre, between 0.1 millimetres and 0.8 millimetres, between 0.1 millimetres and 0.6 millimetres, or between 0.1 millimetres and 0.4 millimetres.

[0295] The solid aerosol-generating film may have a thickness of between 0.2 millimetres and

[0296] 1.2 millimetres, between 0.2 millimetres and 1 millimetre, between 0.2 millimetres and 0.8 millimetres, between 0.2 millimetres and 0.6 millimetres, or between 0.2 millimetres and 0.4 millimetres. The solid aerosol-generating film may have a thickness of between 0.3 millimetres and 1.2 millimetres, between 0.3 millimetres and 1 millimetre, between 0.3 millimetres and 0.8 millimetres, between 0.3 millimetres and 0.6 millimetres, or between 0.3 millimetres and 0.4 millimetres.

[0297] The solid aerosol-generating film may have a basis weight of greater than or equal to 85 grams per square metre, greater than or equal to 100 grams per square metre, greater than or equal to 120 grams per square metre, or greater than or equal to 140 grams per square metre.

[0298] The solid aerosol-generating film may have a basis weight of less than or equal to 300 grams per square metre, less than or equal to 280 grams per square metre, or less than or equal to 260 grams per square metre.

[0299] The solid aerosol-generating film may have a basis weight of between 85 grams per square metre and 300 grams per square metre, between 85 grams per square metre and 280 grams per square metre, or between 85 grams per square metre and 260 grams per square metre.

[0300] The solid aerosol-generating film may have a basis weight of between 100 grams per square metre and 300 grams per square metre, between 100 grams per square metre and 280 grams per square metre, or between 100 grams per square metre and 260 grams per square metre.

[0301] The solid aerosol-generating film may have a basis weight of between 120 grams per square metre and 300 grams per square metre, between 120 grams per square metre and 280 grams per square metre, or between 120 grams per square metre and 260 grams per square metre.

[0302] The solid aerosol-generating film may have a basis weight of between 140 grams per square metre and 300 grams per square metre, between 140 grams per square metre and 280 grams per square metre, or between 140 grams per square metre and 260 grams per square metre.

[0303] The solid aerosol-generating substrate may be a solid aerosol-generating gel.

[0304] Preferably, the solid aerosol-generating gel is substantially tobacco-free.

[0305] More preferably, the solid aerosol-generating gel is tobacco-free.

[0306] Preferably, the aerosol former content of the solid aerosol-generating gel is within the ranges recited above for solid aerosol-generating substrates described as having a relatively high total aerosol former content.

[0307] According to the second aspect of the invention there is provided an aerosol-generating article comprising a solid aerosol-generating substrate according to the first aspect of the invention. The aerosol-generating article may have a geminal dicarboxylic acid content of greater than or equal to 0.25 milligrams, greater than or equal to 0.5 milligrams, or greater than or equal to 0.75 milligrams.

[0308] The aerosol-generating article may have a geminal dicarboxylic acid content of less than or equal to 7 milligrams, less than or equal to 5 milligrams, or less than or equal to 3 milligrams.

[0309] The aerosol-generating article may have a geminal dicarboxylic acid content of between 0.25 milligrams and 7 milligrams, between 0.25 milligrams and 5 milligrams, or between 0.25 milligrams and 3 milligrams.

[0310] The aerosol-generating article may have a geminal dicarboxylic acid content of between 0. 5 milligrams and 7 milligrams, between 0.5 milligrams and 5 milligrams, or between 0.5 milligrams and 3 milligrams.

[0311] The aerosol-generating article may have a geminal dicarboxylic acid content of between 0.75 milligrams and 7 milligrams, between 0.75 milligrams and 5 milligrams, or between 0.75 milligrams and 3 milligrams.

[0312] Aerosol-generating articles according to the second aspect of the invention may have any desired shape. For example, the aerosol-generating article may be substantially cylindrical.

[0313] The aerosol-generating article may have any desired transverse cross-section. For example, the aerosol-generating article may have a substantially circular, oval or elliptical transverse cross-section.

[0314] The aerosol-generating article may have any desired length. For example, the aerosolgenerating article may have a length of between 30 millimetres and 70 millimetres, between 35 millimetres and 65 millimetres, or between 40 millimetres and 60 millimetres.

[0315] The aerosol-generating article may have any desired width. For example, the aerosolgenerating article may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres.

[0316] The aerosol-generating article may comprise an aerosol-generating rod comprising the solid aerosol-generating substrate.

[0317] The aerosol-generating article may include one or more other components.

[0318] The one or more other components may include one or more of an upstream element, a support element, an aerosol-cooling element, and a mouthpiece element.

[0319] The aerosol-generating article may comprise an upstream element located at the distal end of the aerosol-generating article.

[0320] The upstream element may be located immediately upstream of the solid aerosolgenerating substrate.

[0321] The upstream element may advantageously prevent direct contact with the solid aerosolgenerating substrate. Where the aerosol-generating article comprises a susceptor located within the solid aerosol-generating substrate, this may advantageously help to prevent displacement or deformation of the susceptor during transport and handling of the aerosol-generating article.

[0322] The upstream element may comprise a plug of porous material. For example, the upstream element may comprise a cellulose acetate plug.

[0323] The upstream element may have any desired shape. For example, the upstream element may be substantially cylindrical.

[0324] The upstream element may have any desired transverse cross-section. For example, the support element may have a substantially circular, oval or elliptical transverse cross-section.

[0325] The upstream element may have any desired length. For example, the upstream element may have a length of between 1 mm and 10 mm, between 1 mm and 8 mm, or between 1 mm and 6 mm. For example, the upstream element may have a length of between 3 mm and 10 mm, between 3 mm and 8 mm, or between 3 mm and 6 mm.

[0326] The upstream element may have any desired width. For example, the upstream element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The upstream element may have a width that is substantially the same as the width of the aerosol-generating article.

[0327] The aerosol-generating article may comprise a support element located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0328] The support element may be located immediately downstream of the solid aerosolgenerating substrate.

[0329] The support element may comprise a hollow tubular segment. For example, the support element may comprise a hollow cellulose acetate tube.

[0330] The hollow tubular segment may define a longitudinal cavity providing an unrestricted flow channel.

[0331] The support element may have any desired shape. For example, the support element may be substantially cylindrical.

[0332] The support element may have any desired transverse cross-section. For example, the support element may have a substantially circular, oval or elliptical transverse cross-section.

[0333] The support element may have any desired length. For example, the support element may have a length of between 5 mm and 15 mm, between 5 mm and 12 mm, or between 5 mm and 10 mm. For example, the support element may have a length of between 7 mm and 15 mm, between 7 mm and 1 mm, or between 7 mm and 10 mm.

[0334] The support element may have any desired width. For example, the support element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The support element may have a width that is substantially the same as the width of the aerosol-generating article. The aerosol-generating article may comprise a mouthpiece element located at the proximal end of the aerosol-generating article.

[0335] The mouthpiece element may comprise a plug of porous material. For example, the mouthpiece element may comprise a cellulose acetate plug.

[0336] The mouthpiece element may comprise a mouth end cavity.

[0337] The mouth end cavity may be defined by a hollow tubular element provided at the proximal end of the mouthpiece element.

[0338] The mouth end cavity may be defined by a wrapper.

[0339] The mouthpiece element may have any desired shape. For example, the mouthpiece element may be substantially cylindrical.

[0340] The mouthpiece element may have any desired transverse cross-section. For example, the mouthpiece element may have a substantially circular, oval or elliptical transverse crosssection.

[0341] The mouthpiece may have any desired length. For example, the mouthpiece element may have a length of between 5 mm and 20 mm, between 5 mm and 15 mm, or between 5 mm and 10 mm. For example, the mouthpiece element may have a length of between 6 mm and 20 mm, between 6 mm and 15 mm, or between 6 mm and 10 mm. For example, the mouthpiece element may have a length of between 7 mm and 20 mm, between 7 mm and 15 mm, or between 7 mm and 10 mm.

[0342] The mouthpiece element may have any desired width. For example, the mouthpiece element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The mouthpiece element may have a width that is substantially the same as the width of the aerosol-generating article.

[0343] The aerosol-generating article may comprise an aerosol-cooling element located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0344] Where the aerosol-generating article comprises a mouthpiece element, the aerosolcooling element may be located immediately upstream of the mouthpiece element.

[0345] Where the aerosol-generating article comprises a support element, the aerosol-cooling element may be located immediately downstream of the support element.

[0346] The aerosol-cooling element may comprise a hollow tubular segment. For example, the aerosol-cooling element may comprise a hollow cellulose acetate tube.

[0347] The hollow tubular segment may define a longitudinal cavity providing an unrestricted flow channel.

[0348] The aerosol-cooling element may have any desired shape. For example, the aerosolcooling element may be substantially cylindrical. The aerosol-cooling element may have any desired transverse cross-section. For example, the aerosol-cooling element may have a substantially circular, oval or elliptical transverse cross-section.

[0349] The aerosol-cooling element may have any desired length. For example, the aerosolcooling element may have a length of between 5 mm and 20 mm or between 5 mm and 15 mm. For example, the aerosol-cooling element may have a length of between 6 mm and 20 mm or between 6 mm and 15 mm. For example, the aerosol-cooling element may have a length of between 7 mm and 20 mm or between 7 mm and 15 mm.

[0350] The aerosol-cooling element may have any desired width. For example, the aerosolcooling element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The aerosol-cooling element may have a width that is substantially the same as the width of the aerosol-generating article.

[0351] The aerosol-generating article may comprise a susceptor.

[0352] The susceptor may be in direct contact with the solid aerosol-generating substrate.

[0353] The susceptor may be located within an aerosol-generating rod comprising the solid aerosol-generating substrate.

[0354] The susceptor may be located within the solid aerosol-generating substrate.

[0355] The solid aerosol-generating substrate may at least partially surround the susceptor.

[0356] The solid aerosol-generating substrate may be disposed on the susceptor. For example, where the solid aerosol-generating substrate is a solid aerosol-generating film, the susceptor may be at least partially coated with the solid aerosol-generating film.

[0357] The susceptor may be at least partially embedded in the solid aerosol-generating substrate. For example, where the solid aerosol-generating substrate is a solid aerosolgenerating gel, the susceptor may be at least partially embedded in the solid aerosol-generating gel.

[0358] The susceptor may be an elongate susceptor.

[0359] As used herein, the term “elongate” is used to describe a susceptor having a length that is greater than the width thereof. For example, the length of the susceptor may be at least twice the width thereof.

[0360] The susceptor may have any desired length. For example, the susceptor may have a length of between 6 millimetres and 18 millimetres, between 8 millimetres and 16 millimetres, or between 10 millimetres and 14 millimetres.

[0361] The susceptor may have a length that is substantially the same as the length of the solid aerosol-generating substrate or substantially the same as the length of an aerosol-generating rod comprising the solid aerosol-generating substrate. The susceptor may extend along a longitudinal axis of the aerosol-generating article.

[0362] The susceptor may have any desired width. For example, the susceptor may have a width of between 2 millimetres and 8 millimetres, between 3 millimetres and 7 millimetres, or between 4 millimetres and 6 millimetres.

[0363] The susceptor may have any desired thickness. For example, the susceptor may have a thickness of between 30 micrometres and 90 micrometres, between 40 micrometres and 80 micrometres, or between 50 micrometres and 70 micrometres.

[0364] The susceptor element may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the solid aerosol-generating substrate.

[0365] Advantageously, the susceptor may comprise a metal, an alloy or carbon.

[0366] The susceptor may comprise or consist of a ferromagnetic material, for example a ferromagnetic alloy, ferritic iron, or a ferromagnetic steel or stainless steel. A suitable susceptor may comprise or consist of aluminium.

[0367] The susceptor may be formed from 400 series stainless steels, for example grade 410 stainless steel, or grade 420 stainless steel, or grade 430 stainless steel. Different materials will dissipate different amounts of energy when positioned within electromagnetic fields having similar values of frequency and field strength.

[0368] The susceptor may comprise a non-metallic core with a metal layer disposed on the non- metallic core, for example metallic tracks formed on a surface of a ceramic core.

[0369] The susceptor may have a protective outer layer, for example a protective outer ceramic layer or protective outer glass layer.

[0370] The susceptor may comprise a protective outer coating formed by a glass, a ceramic, or an inert metal.

[0371] The solid aerosol-generating substrate and one or more other components of the aerosolgenerating article may be assembled within one or more wrappers to form the aerosol-generating article. For example, the solid aerosol-generating substrate and other components of the aerosolgenerating article may be assembled within one or more wrappers to form an elongate rod.

[0372] Suitable wrappers for use in aerosol-generating articles according to the second aspect of the invention are known in the art and include, but are not limited to: cigarette papers; filter plug wraps; tipping papers; metallised papers; metal foils; and metal foil-paper laminates.

[0373] The aerosol-generating article may comprise a ventilation zone located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0374] Where the aerosol-generating article comprises an aerosol-cooling element, the ventilation zone may be provided at a location along the aerosol-cooling element. The aerosol-generating article may have a ventilation level of greater than or equal to 10 percent, greater than or equal to 15 percent, greater than or equal to 20 percent, or greater than or equal to 25 percent.

[0375] The aerosol-generating article may have a ventilation level of less than or equal to 50 percent, less than or equal to 45 percent, or less than or equal to 40 percent.

[0376] The aerosol-generating article may have a ventilation level of between 10 percent and 50 percent, between 10 percent and 45 percent, or between 10 percent and 40 percent.

[0377] The aerosol-generating article may have a ventilation level of between 15 percent and 50 percent, between 15 percent and 45 percent, or between 15 percent and 40 percent.

[0378] The aerosol-generating article may have a ventilation level of between 20 percent and 50 percent, between 20 percent and 45 percent, or between 20 percent and 40 percent.

[0379] The aerosol-generating article may have a ventilation level of between 25 percent and 50 percent, between 25 percent and 45 percent, or between 25 percent and 40 percent.

[0380] The aerosol-generating article may have a ventilation level of between 30 percent and 50 percent, between 30 percent and 45 percent, or between 30 percent and 40 percent.

[0381] Aerosol-generating articles according to the second aspect of the invention may resemble conventional lit-end cigarettes.

[0382] Aerosol-generating articles according to the second aspect of the invention may be assembled using known methods and machinery.

[0383] According to the third aspect of the invention there is provided an aerosol-generating system comprising: an aerosol-generating article according to the second aspect of the invention; and an aerosol-generating device configured to heat the solid aerosol-generating substrate of the aerosol-generating article.

[0384] The aerosol-generating system may comprise: a consumable aerosol-generating article according to the second aspect of the invention; and a reusable aerosol-generating device configured to heat the solid aerosol-generating substrate of the aerosol-generating article.

[0385] The aerosol-generating device may be a handheld aerosol-generating device.

[0386] The aerosol-generating device may be an electrically-operated aerosol-generating device.

[0387] The aerosol-generating device may comprise a power supply and control electronics.

[0388] The aerosol-generating device may comprise a battery and control electronics.

[0389] The aerosol-generating device may comprise a housing defining a device cavity.

[0390] The device cavity may be configured to receive at least a portion of the aerosol-generating article.

[0391] The device cavity may be configured to receive at least a distal portion of the aerosolgenerating article. The device cavity may be configured to receive at least the solid aerosol-generating substrate of the aerosol-generating article.

[0392] The device cavity may be substantially cylindrical.

[0393] The device cavity may have a substantially circular cross-section.

[0394] The aerosol-generating device may comprise an external heating element.

[0395] The external heating element may be located around a perimeter of the device cavity.

[0396] The external heating element may be a resistive heating element.

[0397] The external heating element may be a susceptor element.

[0398] The aerosol-generating device may comprise an internal heating element for insertion into the aerosol-generating substrate of the aerosol-generating section of the aerosol-generating article.

[0399] The internal heating element may have a pointed end to facilitate insertion of the internal heating element into the aerosol-generating substrate of the aerosol-generating section of the aerosol-generating article.

[0400] The internal heating element may be located within the device cavity.

[0401] The internal heating element may be arranged substantially longitudinally within the device cavity. That is, a longitudinal axis of the internal heating element may be approximately parallel to a longitudinal axis of the device cavity.

[0402] The internal heating element may be arranged centrally within the device cavity. The internal heating element may extend along a longitudinal axis of the device cavity.

[0403] The internal heating element may be a resistive heating element.

[0404] The internal heating element may be a susceptor element.

[0405] The aerosol-generating device may comprise an induction element.

[0406] The induction element may comprise one or more induction coils.

[0407] The induction element may be located around a perimeter of the device cavity.

[0408] Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0409] Example Ex1 : A solid aerosol-generating substrate for use in an aerosol-generating system, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0410] Example Ex2: A solid aerosol-generating substrate according to Example Ex1 wherein the solid aerosol-generating substrate comprises: tobacco material; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid.

[0411] Example Ex3: A solid aerosol-generating substrate according to Example Ex1 or Ex2 wherein the solid aerosol-generating substrate comprises cut filler.

[0412] Example Ex4: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex3 wherein the solid aerosol-generating substrate comprises homogenised tobacco material.

[0413] Example Ex5: A solid aerosol-generating substrate according to Example Ex1 wherein the solid aerosol-generating substrate is substantially tobacco-free.

[0414] Example Ex6: A solid aerosol-generating substrate according to Example Ex1 wherein the solid aerosol-generating substrate is tobacco-free.

[0415] Example Ex7: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex6 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of less than or equal to 300 degrees Celsius.

[0416] Example Ex8: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex6 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of less than or equal to 220 degrees Celsius.

[0417] Example Ex9: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex8 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of greater than or equal to 100 degrees Celsius.

[0418] Example Ex10: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex8 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid capable of undergoing thermal decarboxylation to produce a monocarboxylic acid at a temperature of greater than or equal to 120 degrees Celsius.

[0419] Example Ex11 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex10 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of less than or equal to 300 degrees Celsius.

[0420] Example Ex12: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex10 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of less than or equal to 200 degrees Celsius.

[0421] Example Ex13: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex12 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of greater than or equal to 100 degrees Celsius.

[0422] Example Ex14: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex13 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid selected from benzylmalonic acid, cyclobutane-1 ,1 -dicarboxylic acid, cyclohexane- 1 ,1 - dicarboxylic acid, isopropylmalonic acid, malonic acid, methylmalonic acid, and phenylmalonic acid.

[0423] Example Ex15: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex13 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid selected from malonic acid, benzylmalonic acid, isopropylmalonic acid, methylmalonic acid, and phenylmalonic acid.

[0424] Example Ex16: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex13 wherein the one or more carboxylic acids comprise malonic acid.

[0425] Example Ex17: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex16 wherein the solid aerosol-generating substrate comprises a single carboxylic acid, wherein the single carboxylic acid is a geminal dicarboxylic acid.

[0426] Example Ex18: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex16 wherein the solid aerosol-generating substrate comprises a plurality of carboxylic acids, wherein the plurality of carboxylic acids comprise at least one geminal dicarboxylic acid.

[0427] Example Ex19: A solid aerosol-generating substrate according to Example Ex18 wherein the plurality of carboxylic acids comprise a single geminal dicarboxylic acid.

[0428] Example Ex20: A solid aerosol-generating substrate according to Example Ex18 wherein the plurality of carboxylic acids comprise a plurality of geminal dicarboxylic acids.

[0429] Example Ex21 : A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex20 wherein the plurality of carboxylic acids comprise at least one monocarboxylic acid.

[0430] Example Ex22: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex20 wherein the plurality of carboxylic acids comprise at least one monocarboxylic acid selected from benzoic acid, lactic acid, and levulinic acid.

[0431] Example Ex23: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex22 wherein the plurality of carboxylic acids comprise at least non-geminal dicarboxylic acid.

[0432] Example Ex24: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex22 wherein the plurality of carboxylic acids comprise at least one non-geminal dicarboxylic acid selected from fumaric acid and succinic acid.

[0433] Example Ex25: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.15.

[0434] Example Ex26: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.3.

[0435] Example Ex27: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.5.

[0436] Example Ex28: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.6.

[0437] Example Ex29: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.7.

[0438] Example Ex30: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.8.

[0439] Example Ex31 : A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.85.

[0440] Example Ex32: A solid aerosol-generating substrate according to any one of Examples Ex18 to Ex24 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.9.

[0441] Example Ex33: A solid aerosol-generating substrate according to Example Ex18 wherein all of the plurality of carboxylic acids are geminal dicarboxylic acids.

[0442] Example Ex34: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex33 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content of greater than or equal to 0.4 percent by weight. Example Ex35: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex33 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content of greater than or equal to 0.5 percent by weight.

[0443] Example Ex36: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex33 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content of greater than or equal to 1 percent by weight.

[0444] Example Ex37: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex33 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content of greater than or equal to 1 .5 percent by weight.

[0445] Example Ex38: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex33 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content of greater than or equal to 2 percent by weight.

[0446] Example Ex39: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex38 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content content of less than or equal to 12 percent by weight.

[0447] Example Ex40: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex38 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content content of less than or equal to 8 percent by weight.

[0448] Example Ex41 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex38 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content content of less than or equal to 6 percent by weight.

[0449] Example Ex42: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex38 wherein the solid aerosol-generating substrate has a geminal dicarboxylic acid content content of less than or equal to 4 percent by weight.

[0450] Example Ex43: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex42 wherein the solid aerosol-generating substrate has a total carboxylic acid content of greater than or equal to 0.5 percent by weight.

[0451] Example Ex44: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex42 wherein the solid aerosol-generating substrate has a total carboxylic acid content of greater than or equal to 1 percent by weight.

[0452] Example Ex45: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex42 wherein the solid aerosol-generating substrate has a total carboxylic acid content of greater than or equal to 1 .5 percent by weight.

[0453] Example Ex46: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex42 wherein the solid aerosol-generating substrate has a total carboxylic acid content of greater than or equal to 2 percent by weight. Example Ex47: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex46 wherein the solid aerosol-generating substrate has a total carboxylic acid content of less than or equal to 15 percent by weight.

[0454] Example Ex48: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex46 wherein the solid aerosol-generating substrate has a total carboxylic acid content of less than or equal to 8 percent by weight.

[0455] Example Ex49: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex46 wherein the solid aerosol-generating substrate has a total carboxylic acid content of less than or equal to 6 percent by weight.

[0456] Example Ex50: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex46 wherein the solid aerosol-generating substrate has a total carboxylic acid content of less than or equal to 4 percent by weight.

[0457] Example Ex51 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex50 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 0.25.

[0458] Example Ex52: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex50 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 0.5.

[0459] Example Ex53: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex50 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 1 .

[0460] Example Ex54: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex50 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 2.

[0461] Example Ex55: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex54 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 7.

[0462] Example Ex56: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex54 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 5.

[0463] Example Ex57: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex54 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 4.

[0464] Example Ex58: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex54 wherein a molar ratio of geminal dicarboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 3. Example Ex59: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex58 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 0.5

[0465] Example Ex60: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex58 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 1 .

[0466] Example Ex61 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex58 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 1 .5.

[0467] Example Ex62: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex58 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is greater than or equal to 2.

[0468] Example Ex63: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex62 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 7.

[0469] Example Ex64: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex62 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 5.

[0470] Example Ex65: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex62 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 4.

[0471] Example Ex66: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex62 wherein a molar ratio of total carboxylic acid to nicotine in the solid aerosolgenerating substrate is less than or equal to 3.

[0472] Example Ex67: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex66 wherein the one or more aerosol-formers comprise one or more polyhydric alcohols.

[0473] Example Ex68: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex68 wherein the one or more aerosol-formers comprise one or more polyhydric alcohols selected from 1 ,3-butanediol, glycerine, 1 ,3-propanediol, propylene glycol, and triethylene glycol.

[0474] Example Ex69: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex66 wherein the one or more aerosol-formers comprise one or more polyhydric alcohols selected from glycerine and propylene glycol.

[0475] Example Ex70: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 5 percent by weight. Example Ex71 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 10 percent by weight.

[0476] Example Ex72: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 15 percent by weight.

[0477] Example Ex73: A solid aerosol-generating substrate according to any one of Examples Ex70 to Ex72 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 30 percent by weight.

[0478] Example Ex74: A solid aerosol-generating substrate according to any one of Examples Ex70 to Ex72 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 25 percent by weight.

[0479] Example Ex75: A solid aerosol-generating substrate according to any one of Examples Ex70 to Ex72 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 20 percent by weight.

[0480] Example Ex76: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 40 percent by weight.

[0481] Example Ex77: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 45 percent by weight.

[0482] Example Ex78: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex69 wherein the solid aerosol-generating substrate has a total aerosol former content of greater than or equal to 50 percent by weight.

[0483] Example Ex79 A solid aerosol-generating substrate according to any one of Examples Ex76 to Ex78 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 80 percent by weight.

[0484] Example Ex80: A solid aerosol-generating substrate according to any one of Examples Ex76 to Ex78 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 75 percent by weight.

[0485] Example Ex81 : A solid aerosol-generating substrate according to any one of Examples Ex76 to Ex78 wherein the solid aerosol-generating substrate has a total aerosol former content of less than or equal to 70 percent by weight.

[0486] Example Ex82: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex81 wherein the solid aerosol-generating substrate has a nicotine content of greater than or equal to 0.5 percent by weight. Example Ex83: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex81 wherein the solid aerosol-generating substrate has a nicotine content of greater than or equal to 1 percent by weight.

[0487] Example Ex84: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex81 wherein the solid aerosol-generating substrate has a nicotine content of greater than or equal to 1 .5 percent by weight.

[0488] Example Ex85: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex84 wherein the solid aerosol-generating substrate has a nicotine content of less than or equal to 10 percent by weight.

[0489] Example Ex86: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex84 wherein the solid aerosol-generating substrate has a nicotine content of less than or equal to 5 percent by weight.

[0490] Example Ex87: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex84 wherein the solid aerosol-generating substrate has a nicotine content of less than or equal to 4 percent by weight.

[0491] Example Ex88: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex84 wherein the solid aerosol-generating substrate has a nicotine content of less than or equal to 3 percent by weight.

[0492] Example Ex89: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex88 wherein the solid aerosol-generating substrate comprises one or more cellulose based agents.

[0493] Example Ex90: A solid aerosol-generating substrate according to Example Ex89 wherein the solid aerosol-generating substrate has a total cellulose based agent content of greater than or equal to 25 percent by weight.

[0494] Example Ex91 : A solid aerosol-generating substrate according to Example Ex89 wherein the solid aerosol-generating substrate has a total cellulose based agent content of greater than or equal to 30 percent by weight.

[0495] Example Ex92: A solid aerosol-generating substrate according to Example Ex89 wherein the solid aerosol-generating substrate has a total cellulose based agent content of greater than or equal to 35 percent by weight.

[0496] Example Ex93: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex92 wherein the solid aerosol-generating substrate has a total cellulose based agent content of less than or equal to 55 percent by weight.

[0497] Example Ex94: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex92 wherein the solid aerosol-generating substrate has a total cellulose based agent content of less than or equal to 50 percent by weight. Example Ex95: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex92 wherein the solid aerosol-generating substrate has a total cellulose based agent content of less than or equal to 45 percent by weight.

[0498] Example Ex96: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex95 wherein the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents or cellulose based binding agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), hydroxyethyl cellulose (HEC), hydroxyethyl methylcellulose (HEMC), hydroxypropyl cellulose (HPC), hydroxypropyl methylcellulose (HPMC), and methylcellulose (MC).

[0499] Example Ex97: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex95 wherein the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents or cellulose binding agents selected from carboxymethyl cellulose (CMC), ethylcellulose (EC), methylcellulose (MC), and hydroxypropyl methylcellulose (HPMC).

[0500] Example Ex98: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex95 wherein the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents or cellulose based binding agents selected from carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC).

[0501] Example Ex99: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex98 wherein the solid aerosol-generating substrate comprises one or more cellulose based strengthening agents.

[0502] Example Ex100: A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex98 wherein the solid aerosol-generating substrate comprises one or more cellulose based strengthening agents selected from cellulose fibres, cellulose powder, and microcrystalline cellulose (MCC).

[0503] Example Ex101 : A solid aerosol-generating substrate according to any one of Examples Ex89 to Ex98 wherein the solid aerosol-generating substrate comprises cellulose fibres.

[0504] Example Ex102: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex101 wherein the solid aerosol-generating substrate comprises a plurality of thermally conductive carbon particles.

[0505] Example Ex103: A solid aerosol-generating substrate according to Example Ex102 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of greater than or equal to 10 percent by weight.

[0506] Example Ex104: A solid aerosol-generating substrate according to Example Ex102 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of greater than or equal to 20 percent by weight. Example Ex105: A solid aerosol-generating substrate according to Example Ex102 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of greater than or equal to 30 percent by weight.

[0507] Example Ex106: A solid aerosol-generating substrate according to any one of Examples Ex102 to Ex105 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of less than or equal to 90 percent by weight.

[0508] Example Ex107: A solid aerosol-generating substrate according to any one of Examples Ex102 to Ex105 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of less than or equal to 80 percent by weight.

[0509] Example Ex108: A solid aerosol-generating substrate according to any one of Examples Ex102 to Ex105 wherein the solid aerosol-generating substrate has a total thermally conductive carbon particle content of less than or equal to 70 percent by weight.

[0510] Example Ex109: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex108 wherein the solid aerosol-generating substrate is non-colloidal.

[0511] Example Ex110: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex109 wherein the solid aerosol-generating substrate remains solid when heated to a temperature of between 180 degrees Celsius and 350 degrees Celsius.

[0512] Example Ex11 1 : A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex109 wherein the solid aerosol-generating substrate remains solid when heated to a temperature of between 200 degrees Celsius and 320 degrees Celsius.

[0513] Example Ex112: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex109 wherein the solid aerosol-generating substrate remains solid when heated to a temperature of between 220 degrees Celsius and 300 degrees Celsius.

[0514] Example Ex113: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex109 wherein the solid aerosol-generating substrate remains solid when heated to a temperature of between 240 degrees Celsius and 280 degrees Celsius.

[0515] Example Ex114: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex113 wherein the solid aerosol-generating substrate solid aerosol-generating substrate is in the form of a sheet.

[0516] Example Ex115: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex1 13 wherein the solid aerosol-generating substrate is in the form of a hollow tubular element.

[0517] Example Ex116: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex1 13 wherein the solid aerosol-generating substrate is in the form of a plurality of strands.

[0518] Example Ex:1 17 A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex116 wherein the solid aerosol-generating substrate is a solid aerosol-generating film. Example Ex118: A solid aerosol-generating substrate according to any one of Examples Ex1 to Ex116 wherein the solid aerosol-generating substrate is a solid aerosol-generating gel.

[0519] Example Ex119: An aerosol-generating article for use in an aerosol-generating system, the aerosol-generating article comprising a solid aerosol-generating substrate according to any one of Examples Ex1 to Ex118.

[0520] Example Ex120: An aerosol-generating article according to Example Ex119 wherein the aerosol-generating article comprises an upstream element located at a distal end of the aerosolgenerating article.

[0521] Example Ex121 : An aerosol-generating article according to Example Ex1 19 or Ex120 wherein the aerosol-generating article comprises a support element located between the solid aerosol-generating substrate and a proximal end of the aerosol-generating article.

[0522] Example Ex122: An aerosol-generating article according to any one of Examples Ex119 to Ex121 wherein the aerosol-generating article comprises an aerosol-cooling element located between the solid aerosol-generating substrate and a proximal end of the aerosol-generating article.

[0523] Example Ex123: A solid aerosol-generating article according to any one of Examples Ex119 to Ex122 wherein the aerosol-generating article comprises a mouthpiece element located at a proximal end of the aerosol-generating article.

[0524] Example Ex124: A solid aerosol-generating article according to any one of Examples Ex119 to Ex123 wherein the aerosol-generating article comprises a susceptor.

[0525] Example Ex125: A solid aerosol-generating article according to Example Ex124 wherein the susceptor is in direct contact with the solid aerosol-generating substrate.

[0526] Example Ex126: A solid aerosol-generating article according to Example Ex124 or Ex125 wherein the susceptor is located within an aerosol-generating rod comprising the solid aerosolgenerating substrate.

[0527] Example Ex127: A solid aerosol-generating article according to any one of Examples Ex124 or Ex126 wherein the susceptor is located within the solid aerosol-generating substrate.

[0528] Example Ex128: A solid aerosol-generating article according to any one of Examples Ex124 or Ex127 wherein the solid aerosol-generating substrate at least partially surrounds the susceptor.

[0529] Example Ex129: A solid aerosol-generating article according to any one of Examples Ex124 or Ex127 wherein the solid aerosol-generating substrate is disposed on the susceptor.

[0530] Example Ex130: A solid aerosol-generating article according to any one of Examples Ex124 or Ex127 wherein the susceptor is at least partially embedded in the solid aerosolgenerating substrate. Example Ex131 : An aerosol-generating system comprising: an aerosol-generating article according to any one of Examples Ex1 19 to Ex130; and an aerosol-generating device configured to heat the solid aerosol-generating substrate of the aerosol-generating article.

[0531] The invention will now be further described, by way of example only, with reference to the following examples and accompanying drawings, in which:

[0532] Figure 1 shows a schematic cross-sectional view of an embodiment of an aerosolgenerating article according to the second aspect of the invention comprising a solid aerosolgenerating substrate according to the first aspect of the invention; and

[0533] Figure 2 shows a schematic cross-sectional view of an embodiment of an aerosolgenerating system according to the third aspect of the invention comprising the aerosolgenerating article shown in Figure 2 and an electrically-operated aerosol-generating device comprising an inductor.

[0534] Figures 3a and 3b show graphs of harshness in mouth and throat intensity versus puff number and impact in chest impact intensity versus puff number for inhalable aerosols generated by heating a solid aerosol-generating substrate according to an embodiment of the first aspect of the invention and a comparative solid aerosol-generating substrate not according to the first aspect of the invention; and

[0535] Figures 4a and 4b show graphs of harshness in mouth and throat intensity versus puff number and impact in chest impact intensity versus puff number for inhalable aerosols generated by heating a solid aerosol-generating substrate according to another embodiment of the first aspect of the invention and two comparative solid aerosol-generating substrate not according to the first aspect of the invention.

[0536] The aerosol-generating article 10 shown in Figure 1 comprises an aerosol-generating rod 12, a proximal section 14 located downstream of the aerosol-generating rod 12 and a distal section 16 located upstream of the aerosol-generating rod 12. As shown in Figure 1 , the aerosolgenerating article 10 has an upstream or distal end 18 and a downstream or proximal end 20. The aerosol-generating article 10 may have an overall length of 45 millimetres and an external diameter of 7.2 millimetres.

[0537] The proximal section 14 of the aerosol-generating article 10 comprises a support element 22 located immediately downstream of the aerosol-generating rod 12, an aerosol-cooling element 24 located immediately downstream of the support element 22, and a mouthpiece element 42 located immediately downstream of the aerosol-cooling element 24. The support element 22 and the aerosol-cooling element 24 together define an intermediate hollow section 50 of the aerosolgenerating article 10.

[0538] The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an internal cavity 28 that extends from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 20. The first hollow tubular segment 26 may have a length of 8 millimetres and an external diameter of 6.9 millimetres. The first hollow tubular segment 26 may have an internal diameter of 1 .9 millimetres.

[0539] The aerosol-cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an internal cavity 36 that extends from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The second hollow tubular segment 34 may have a length of 13 millimetres and an external diameter of 6.9 millimetres. The second hollow tubular segment

[0540] 34 may have an internal diameter of 3.25 millimetres.

[0541] As shown by the dashed vertical line in Figure 1 , the aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. The ventilation zone may be provided 2 millimetres from the upstream end of the second hollow tubular segment 34. A ventilation level of the aerosol-generating article 10 may be

[0542] 35 percent.

[0543] The mouthpiece element 42 is in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 42 may have a length of 7 millimetres and an external diameter of 6.9 millimetres.

[0544] The aerosol-generating rod 12 comprises a gathered crimped paper sheet coated with a solid aerosol-generating substrate. The solid aerosol-generating substrate is a solid aerosolgenerating film having the composition shown in Example B. The aerosol-generating rod 12 may have a length of 12 millimetres and an external diameter of 6.9 millimetres.

[0545] The aerosol-generating article 10 comprises an elongate susceptor 44 located within the aerosol-generating rod 12. As shown in Figure 2, the elongate susceptor 44 is surrounded by the gathered crimped paper sheet coated with the solid aerosol-generating film and extends along the longitudinal axis of the aerosol-generating rod 12 from an upstream end of the aerosolgenerating rod 12 to a downstream end of the aerosol-generating rod 12. The elongate susceptor 44 is in direct contact with the solid aerosol-generating film. The elongate susceptor 44 may be in the form of a strip having a length of 12 millimetres, a width of 5 millimetres and a thickness of 60 micrometres.

[0546] The distal section 16 of the aerosol-generating article 10 comprises an upstream element 46 located immediately upstream of the aerosol-generating rod 12. The upstream element 46 is in the form of a cylindrical plug of cellulose acetate circumscribed by a stiff wrapper. The upstream element 46 may have a length of 5 millimetres and an external diameter of 6.9 millimetres.

[0547] It will be appreciated that the aerosol-generating article 10 shown Figure 1 is only one example of an embodiment of an aerosol-generating article according to the first aspect of the invention and that other embodiments are possible.

[0548] The aerosol-generating system 100 shown in Figure 2 comprises the aerosol-generating article 10 shown in Figure 1 and a handheld electrically operated aerosol-generating device 1 10.

[0549] The aerosol-generating device 110 comprises a housing 1 12 defining a device cavity 1 14 configured to receive a distal portion of the aerosol-generating article 10.

[0550] The aerosol-generating device 110 comprises an inductor 116 configured to heat the solid aerosol-generating film in the aerosol-generating rod 12 of the aerosol-generating article 10 when the distal portion of the aerosol-generating article 10 is received in the device cavity 114.

[0551] The aerosol-generating device also comprises a power supply in the form of a battery (not shown), such as a rechargeable lithium ion battery, and control circuitry (not shown).

[0552] The inductor 1 16 comprises an induction coil. The control circuitry controls the supply of electrical power from the battery to the induction coil.

[0553] In use, a fluctuating or alternating electromagnetic field produced by the induction coil of the inductor 116 induces eddy currents in the elongate susceptor 44 in the aerosol-generating rod 12 of the aerosol-generating article 10, causing the elongate susceptor 44 to heat up. Heat generated in the elongate susceptor 44 is transferred to the solid aerosol-generating film in the aerosol-generating rod 12 of the aerosol-generating article 10 by conduction.

[0554] The user draws on the mouthpiece element 42 of the aerosol-generating article 10. When a user draws on the mouthpiece 142, air is drawn into the aerosol-generating article 10 through the distal end 18. The drawn air passes through the upstream element 46 to the aerosolgenerating rod 12. Heating of the solid aerosol-generating film releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn air as it flows through the aerosol-generating rod 12. The drawn air and entrained aerosol pass through the intermediate hollow section 50 of the aerosol-generating article 10, where they cool and condense. The cooled aerosol then passes through the mouthpiece element 42 of the aerosol-generating article 10 into the mouth of the user. Examples

[0555] Comparative Example A and Example B

[0556] A solid aerosol-generating substrate not according to the first aspect of the invention is produced having the composition shown in Comparative Example A below.

[0557] The solid aerosol-generating substrate of Comparative Example A is prepared by:

[0558] (1 ) mixing the components together with water using agitation to form a slurry;

[0559] (2) casting a layer of the slurry onto a plane surface to form a film having a thickness of between 600 and 1000 micrometres;

[0560] (3) leaving the film on the plane surface to solidify; and

[0561] (3) drying the film by heating the film to 140 degrees Celsius for 8 minutes to form a solid aerosol-generating film.

[0562] A solid aerosol-generating substrate according to the first aspect of the invention is produced having the composition shown in Example B below. The solid aerosol-generating substrate according to the first aspect of the invention of Example B is prepared by injecting the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A with 1 .2 mg of malonic acid (12 microlitres of a 10% aqueous solution of malonic acid).

[0563] The solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A and the solid aerosol-generating substrate according to the first aspect of the invention of Example B are heated to a temperature of between 250 degrees Celsius and 260 degrees Celsius to generate inhalable aerosols.

[0564] The harshness in mouth and throat intensity and the impact in chest intensity for the inhalable aerosols generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A and the solid aerosol-generating substrate according to the first aspect of the invention of Example B are assessed by nine panellists as a function of puff number over 12 puffs. The averaged results are shown in Figures 3a and 3b in which a value of ten on the y axis indicates a high intensity and a value of zero on the y axis indicates no intensity. In Figure 3a and 3b, the puff-by-puff measurements for the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A are shown by circles and the puff-by- puff measurements for the solid aerosol-generating substrate according to the first aspect of the invention of Example B are shown by squares.

[0565] As shown in Figure 3a, inclusion of malonic acid in the solid aerosol-generating substrate according to the first aspect of the invention of Example B advantageously results in a significant decrease in harshness in mouth and throat intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A. As shown in Figure 3b, inclusion of malonic acid in the solid aerosol-generating substrate according to the first aspect of the invention of Example B also advantageously results in a significant decrease in impact in chest intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example A.

[0566] Comparative Examples C and E and Example D

[0567] A solid aerosol-generating substrate not according to the first aspect of the invention is produced having the composition shown in Comparative Example C below.

[0568] The solid aerosol-generating substrate of Comparative Example C is prepared by:

[0569] (1) mixing the components together with water using agitation to form a slurry;

[0570] (2) casting a layer of the slurry onto a plane surface to form a film having a thickness of between 600 and 1000 micrometres;

[0571] (3) leaving the film on the plane surface to solidify; and

[0572] (3) drying the film by heating the film to 1 0 degrees Celsius to 140 degrees Celsius for 2-5 minutes to form a solid aerosol-generating film.

[0573] A solid aerosol-generating substrate not according to the first aspect of the invention is produced having the composition shown in Comparative Example D below. The solid aerosolgenerating substrate not according to the first aspect of the invention of Comparative Example D is prepared by injecting the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C with 0.6 mg of acetic acid (12 microlitres of a 5% aqueous solution of acetic acid).

[0574] A solid aerosol-generating substrate according to the first aspect of the invention is produced having the composition shown in Example E below. The solid aerosol-generating substrate according to the first aspect of the invention of Example E is prepared by injecting the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C with 1 .2 mg of malonic acid (12 microlitres of a 10% aqueous solution of malonic acid).

[0575]

[0576] The solid aerosol-generating substrates not according to the first aspect of the invention of Comparative Examples C and E and the solid aerosol-generating substrate according to the first aspect of the invention of Example D are heated to a temperature of between 250 degrees Celsius and 260 degrees Celsius to generate inhalable aerosols.

[0577] The harshness in mouth and throat intensity and the impact in chest intensity for the inhalable aerosols generated by heating the solid aerosol-generating substrates not according to the first aspect of the invention of Comparative Examples C and E and the solid aerosolgenerating substrate according to the first aspect of the invention of Example D are assessed by eight panellists as a function of puff number over 12 puffs. The averaged results are shown in Figures 4a and 4b in which a value of ten on the y axis indicates a high intensity and a value of zero on the y axis indicates no intensity. In Figure 4a and 4b, the puff-by-puff measurements for the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C are shown by squares, the puff-by- puff measurements for the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example E are shown by triangles, and the puff-by-puff measurements for the solid aerosol-generating substrate according to the first aspect of the invention of Example D are shown by circles.

[0578] As shown in Figure 4a, inclusion of malonic acid in the solid aerosol-generating substrate according to the first aspect of the invention of Example D advantageously results in a significant decrease in harshness in mouth and throat intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C. As also shown in Figure 4a, inclusion of acetic acid in the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example E is significantly less effective in reducing harshness in mouth and throat intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrates not according to the first aspect of the invention of Comparative Example C, particularly in later puffs.

[0579] As shown in Figure 4b, inclusion of malonic acid in the solid aerosol-generating substrate according to the first aspect of the invention of Example D also advantageously results in a significant decrease in chest impact intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C. As also shown in Figure 4b, inclusion of acetic acid in the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example E is significantly less effective in reducing chest impact intensity of the inhalable aerosol generated by heating thereof compared to the inhalable aerosol generated by heating the solid aerosol-generating substrate not according to the first aspect of the invention of Comparative Example C, particularly in later puffs.

[0580] The specific embodiments and examples described above illustrate, but do not limit, the invention. It is to be understood that other embodiments of the invention may be made and the specific embodiments and examples described herein are not exhaustive.

[0581] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS:1 . A solid aerosol-generating substrate for use in an aerosol-generating system, the solid aerosol-generating substrate comprising: nicotine; one or more aerosol formers; and one or more carboxylic acids, wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid, wherein the solid aerosol-generating substrate is substantially tobacco-free, and wherein the solid aerosol-generating substrate is in the form of a sheet or a plurality of strands.

2. A solid aerosol-generating substrate according to claim 1 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid at a temperature of between 100 degrees Celsius and 300 degrees Celsius.

3. A solid aerosol-generating substrate according to claim 1 or 2 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid that undergoes thermal decarboxylation to produce a monocarboxylic acid having a boiling point of between 100 degrees Celsius and 300 degrees Celsius.

4. A solid aerosol-generating substrate according to any one of claims 1 to 3 wherein the one or more carboxylic acids comprise at least one geminal dicarboxylic acid selected from malonic acid, benzylmalonic acid, isopropylmalonic acid, methylmalonic acid, and phenylmalonic acid.

5. A solid aerosol-generating substrate according to any one of claims 1 to 4 wherein the one or more carboxylic acids comprise malonic acid.

6. A solid aerosol-generating substrate according to any one of claims 1 to 5 wherein a ratio of the weight percent geminal dicarboxylic acid content of the solid aerosol-generating substrate to the weight percent total carboxylic acid content of the solid aerosol-generating substrate is greater than or equal to 0.85.

7. A solid aerosol-generating substrate according to any one of claims 1 to 6 having a geminal dicarboxylic acid content of between 0.5 percent by weight and 12 percent by weight.

8. A solid aerosol-generating substrate according to any one of claims 1 to 7 wherein the solid aerosol-generating substrate has a tobacco content of less than 0.5 percent by weight.

9. A solid aerosol-generating substrate according to any one of claims 1 to 8 wherein the solid aerosol-generating substrate is a solid aerosol-generating film.

10. A solid aerosol-generating substrate according to any one of claims 1 to 9 wherein the solid aerosol-generating substrate is tobacco-free.1 1. A solid aerosol-generating substrate according to any one of claims 1 to 10 having a total aerosol former content of between 40 percent by weight and 80 percent by weight.1 . A solid aerosol-generating substrate according to any one of claims 1 to 11 wherein the solid aerosol-generating substrate comprises one or more cellulose based agents.

13. A solid aerosol-generating substrate according to any one of claims 1 to 12 wherein the solid aerosol-generating substrate comprises one or more cellulose based film-forming agents.

14. An aerosol-generating article for use in an aerosol-generating system, the aerosolgenerating article comprising a solid aerosol-generating substrate according to any one of claims 1 to 13.

15. An aerosol-generating system comprising: an aerosol-generating article according to claim 14; and an aerosol-generating device configured to heat the solid aerosol-generating substrate of the aerosol-generating article.

Images