Aerosol-generating article with upstream combustion-preventing element

Abstract

The aerosol-generating article (10) comprises an aerosol-generating element comprising a rod (12) of aerosol-generating substrate surrounded by a rod plug wrap, an upstream element (48) located upstream from the aerosol-generating element, the upstream element (48) comprising a segment of material (50) surrounded by a first wrapper (52), and a second wrapper (54) surrounding both the upstream element (48) and the aerosol-generating element. The first wrapper (52) or the second wrapper (54), or both, contain a flame-retardant composition along the segment of material (50) of the upstream element (48).

Description

[Technical Field]

[0001] The present invention relates to an aerosol-generating article comprising an aerosol-generating element and adapted to generate an inhalable aerosol upon heating. In particular, the present invention relates to an aerosol-generating article comprising an upstream element located upstream of the aerosol-generating element. Aspects of the present disclosure further relate to an aerosol generation system comprising a heating device and an aerosol-generating article of the type described above. [Background technology]

[0002] Aerosol-generating articles in which an aerosol-generating element, such as a tobacco-containing substrate, is heated rather than combusted, are known in the art. Typically, in such heated smoking articles, the aerosol is generated by transferring heat from a heat source to a physically separated aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and are entrained in the air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.

[0003] Several aerosol generating devices for consuming aerosol-generating articles have been disclosed in the art. Such devices include, for example, electrically heated aerosol generating devices in which an aerosol is generated by heat transfer from one or more electric heater elements of the aerosol generating device to an aerosol-generating element of the aerosol-generating article. For this purpose, the aerosol-generating article is partially received within a heated cavity of the aerosol generating device, such that the upstream end of the aerosol-generating article is inserted into the cavity, while the downstream end of the aerosol-generating article protrudes outside the cavity. For example, an electrically heated aerosol generating device has been proposed that includes an internal heater blade adapted to be inserted into an aerosol-generating substrate when the aerosol-generating article is received within the heated cavity.

[0004] Alternatively, inductively heated aerosol-generating articles are proposed in WO 2015 / 176898. These aerosol-generating articles comprise an aerosol-generating element comprising an aerosol-generating substrate, such as a tobacco-containing substrate, and a susceptor disposed within the aerosol-generating substrate. Functional coupling between the susceptor and the induction heater element of the aerosol-generating device is achieved when the aerosol-generating article is partially received within the heating cavity of the aerosol-generating device.

[0005] Aerosol-generating articles of the types described above typically include one or more additional elements assembled with the aerosol-generating element, usually by one or more wrappers. Each individual element forming part of the aerosol-generating article may have its own wrapper (a so-called "plug wrap"). Two or more of the individual elements may be combined together by an "outer" wrapper. Examples of such additional elements include, but are not limited to, a mouthpiece segment (e.g., in the form of a plug of fibrous material such as cellulose acetate) disposed at the downstream end of the aerosol-generating article, a leading element, i.e., an element disposed at the upstream end of the aerosol-generating article, and a cooling element adapted to advantageously cool the aerosol generated upon heating the aerosol-generating substrate before it reaches the mouthpiece segment. When present, the mouthpiece segment is often attached to the rest of the aerosol-generating article by tipping paper to mimic the typical appearance of a conventional smoking article.

[0006] During use, aerosol-generating articles of the above type are exposed to heat provided by a heater element. Under these conditions, conventional paper wrappers can be prone to scorching or carbonization. To prevent this, and because it is desirable to maintain a consistent visual impression of the aerosol-generating article after use, it has been proposed to combine a metal foil, such as aluminum foil, with a paper layer to provide a wrapper capable of withstanding prolonged exposure to high temperatures. Furthermore, the use of a paper-metal foil laminate has been found to enhance safety and prevent paper combustion or paper pyrolysis products from being delivered to the consumer during use of the aerosol-generating article.

[0007] There is a generally felt need to provide new and improved aerosol-generating articles that are easier to dispose of and have a reduced impact on the environment. Even more desirably, it would be beneficial to provide such aerosol-generating articles that are adapted to prevent the aerosol-generating article from scorching or charring during use. Summary of the Invention

[0008] The present disclosure relates to an aerosol-generating article for generating an aerosol upon heating.

[0009] The aerosol-generating article may comprise an aerosol-generating element.

[0010] The aerosol-generating element may comprise a rod of aerosol-generating substrate.The aerosol-generating element may comprise a rod plug wrap surrounding the rod of aerosol-generating substrate.

[0011] The aerosol-generating article may comprise an upstream element located upstream of the aerosol-generating element.

[0012] The upstream element may comprise a segment of material. The upstream element may comprise a first wrapper surrounding the segment of material. The first wrapper may include a flame retardant composition at a location along the segment of material of the upstream element.

[0013] The aerosol-generating article may include a second wrapper surrounding both the upstream element and the aerosol-generating element, and the second wrapper may include a flame retardant composition at a location along the segment of material of the upstream element.

[0014] According to a first aspect of the present invention, there is provided an aerosol-generating article for generating an aerosol upon heating. The aerosol-generating article comprises an aerosol-generating element comprising a rod of aerosol-generating substrate surrounded by a rod plug wrap. The aerosol-generating article further comprises an upstream element located upstream of the aerosol-generating element, the upstream element comprising a segment of material surrounded by a first wrapper. The aerosol-generating article further comprises a second wrapper surrounding both the upstream element and the aerosol-generating element. The first wrapper, the second wrapper, or both, comprise a flame-retardant composition comprising one or more flame-retardant compounds located along the segment of material of the upstream element.

[0015] As used herein in connection with the present invention, the term "aerosol-generating article" is used to describe an article that includes an aerosol-generating substrate that is heated to generate and deliver an inhalable aerosol to a user.

[0016] As used herein in connection with the present invention, the term "aerosol-generating substrate" is used to describe a substrate that includes an aerosol-forming material that is capable of releasing, upon heating, a volatile compound that is capable of generating an aerosol.

[0017] As used herein in connection with the present invention, 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. Aerosols can be visible or invisible. Aerosols may contain not only vapors of substances that are normally liquids or solids at room temperature, but also solid particles or liquid droplets, or a combination of solid particles and liquid droplets.

[0018] As used herein in connection with the present invention, the term "aerosol-generating device" is used to describe a device that interacts with the aerosol-generating substrate of an aerosol-generating article to generate an aerosol.

[0019] The aerosol-generating article according to the present invention has a proximal end through which the aerosol exits the aerosol-generating article for delivery to a user during use. The proximal end of the aerosol-generating article may also be referred to as the downstream end or mouth end of the aerosol-generating article. During use, a user directly or indirectly breathes on the proximal end of the aerosol-generating article to inhale the aerosol generated by the aerosol-generating article.

[0020] The aerosol-generating article according to the present invention has a distal end. The distal end is opposite the proximal end. The distal end of the aerosol-generating article may also be referred to as the upstream end of the aerosol-generating article.

[0021] Components of an aerosol-generating article according to the present invention may be described as being upstream or downstream of one another based on their relative location between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article.

[0022] As used herein in relation to this specification, the term "longitudinal direction" is used to describe the direction between the upstream and downstream ends of the aerosol-generating article. During use, air is drawn longitudinally through the aerosol-generating article.

[0023] As used herein in connection with the present invention, the term "length" is used to describe the greatest dimension along the longitudinal axis of an aerosol-generating article or a component of an aerosol-generating article.

[0024] As used herein in connection with the present invention, the term "transverse" is used to describe a direction perpendicular to the longitudinal axis. Unless otherwise specified, a "cross section" of an aerosol-generating article or a component of an aerosol-generating article refers to a cross section.

[0025] As used herein in connection with the present invention, the term "width" refers to the largest transverse dimension of an aerosol-generating article or a component of an aerosol-generating article. If the aerosol-generating article has a substantially circular cross-section, the width of the aerosol-generating article corresponds to the diameter of the aerosol-generating article. If the component of the aerosol-generating article has a substantially circular cross-section, the width of the component of the aerosol-generating article corresponds to the diameter of the component of the aerosol-generating article.

[0026] As used herein in connection with the present invention, the term "hollow tubular element" is used to describe a generally cylindrical element having a tubular space along its longitudinal axis. The tubular portion may be generally circular, oval, or elliptical in cross section. The tubular space may be generally circular, oval, or elliptical in cross section. Specifically, the term "hollow tubular element" is used to describe an element that defines at least one airflow conduit that establishes uninterrupted fluid communication between an upstream end of the hollow tubular element and a downstream end of the hollow tubular element.

[0027] Unless otherwise specified, the resistance to draw (RTD) of a component or aerosol-generating article according to the present invention is measured in accordance with ISO 6565-2015. RTD refers to the pressure required to force air through the entire length of the component. The terms "pressure drop" or "draw resistance" of a component or article may also refer to "resistance to draw." These terms generally refer to measurements in accordance with ISO 6565-2015, typically performed at a temperature of about 22 degrees Celsius, a pressure of about 101 kPa (about 760 Torr), and a relative humidity of about 60%, with a volumetric flow rate of about 17.5 milliliters per second at the output or downstream end of the component being measured.

[0028] The "resistance to draw per unit length (RTD)" of a particular component (or element) of an aerosol-generating article, such as an upstream element or an aerosol-generating element, can be calculated by dividing the measured resistance to draw of the component by the total axial length of the component. RTD per unit length refers to the pressure required to force air through unit length of the component. Throughout this disclosure, unit length refers to a length of 1 millimeter. Thus, to derive the RTD per unit length of a particular part, a particular length of the component, for example, a 15 millimeter specimen, can be used for measurement. The RTD of such a specimen is measured in accordance with ISO 6565-2015. For example, if the measured RTD is about 15 millimeters HO, then the RTD per unit length of the component is about 1 millimeter HO / millimeter. The RTD per unit length of a component will generally depend, among other factors, on the structural properties of the materials used in the component, as well as the cross-sectional shape or geometry of the component.

[0029] As briefly described above, an aerosol-generating article according to an embodiment of the present invention comprises an aerosol-generating element and an upstream element located upstream of the aerosol-generating element, the upstream element comprising a segment of material surrounded by a first wrapper. In the aerosol-generating article, a second wrapper surrounds both the upstream element and the aerosol-generating element, e.g., to join them. In contrast to existing aerosol-generating articles, one or both of the first wrapper and the second wrapper includes a flame-retardant composition comprising one or more flame-retardant compounds at a location along the segment of material of the upstream element.

[0030] Surrounding the upstream element with a wrapper containing a flame-retardant composition at a position along the segment of material of the upstream element is beneficial in that it helps prevent combustion of the upstream element. As a result, if a user attempts to light an aerosol-generating article according to the present invention at its distal end, as with a conventional cigarette, the combustion front will be stopped before reaching the aerosol-generating element. Thus, improper use of an aerosol-generating article intended to be heated in a dedicated device to generate an inhalable aerosol is desirably prevented.

[0031] Furthermore, by surrounding the upstream element with a wrapper containing a flame-retardant composition along the material segment of the upstream element, it is possible to advantageously prevent charring or scorching of the wrapper or the wrapper and the underlying material segment upon heating during the intended use of the aerosol-generating article in combination with a heating device. This desired effect is achieved without the need for an additional layer of metal foil or other heat-shielding material within the article. In particular, the inventors have found that by using a wrapper in accordance with the present invention, it is possible to substantially prevent charring or scorching of the wrapper or the underlying material segment when the upstream element is exposed to temperatures ranging from 150 to 370 degrees Celsius. This is advantageous in both aerosol-generating devices in which heat is supplied by a resistive heater element inserted in an aerosol-generating substrate, which can reach temperatures approaching 350 degrees Celsius, and in aerosol-generating devices in which heat is supplied inductively by a susceptor element embedded in an aerosol-generating substrate, which can reach temperatures approaching 260 degrees Celsius.

[0032] The aerosol-generating article according to the present invention does not need to include a metal foil layer as a heat shield, as is common in existing aerosol-generating articles, and therefore is easier to dispose of after use, reducing its impact on the environment.

[0033] The above-mentioned advantageous effects are particularly welcome in embodiments of the aerosol-generating article in which the upstream element is formed entirely or mainly from easily combustible materials such as crimped paper and / or cardboard, which represent a more environmentally friendly and cost-effective alternative to other known materials. The use of a flame-retardant composition according to the invention in place of the metal foil strip further enhances the already high level of environmental compatibility of the overall article.

[0034] By adjusting the amount of flame retardant composition in or on the wrapper (e.g., in terms of amount per square meter of surface area of ​​the wrapper substrate), the extent to which the surface of the wrapper is treated with the flame retardant composition, as well as the formulation of the flame retardant composition itself, it is possible to advantageously increase the flame retardancy of the distal portion of the aerosol-generating article and, to some extent, the flame retardancy of the entire aerosol-generating article.

[0035] Aerosol-generating articles according to the present invention can be manufactured efficiently and rapidly without requiring extensive modifications to existing equipment.

[0036] In some embodiments, the first wrapper comprises a wrapping substrate, and the flame retardant composition is provided on a surface of the wrapping substrate facing the segment of material of the upstream element, a surface of the wrapping substrate facing away from the segment of material of the upstream element, or both.

[0037] The second wrapper preferably comprises a wrapping substrate, and the flame retardant composition is provided on a surface of the wrapping substrate facing the segment of material of the upstream element, on a surface of the wrapping substrate facing away from the segment of material of the upstream element, or both.

[0038] Therefore, many different possible arrangements are possible. Providing the flame retardant composition near or far from the segment of material of the upstream element can have some effect in that some of the flame retardant composition can migrate more or less easily into the segment of material. In the context of the present invention, some migration of the flame retardant composition into the segment of material can be advantageous in that it can further contribute to preventing combustion of the segment of material in the event of misuse of the aerosol-generating article.

[0039] As briefly described above, in an aerosol-generating article according to the present invention, the wrapper surrounding the upstream element includes a flame-retardant composition containing one or more flame-retardant compounds at a location along the material segment of the upstream element. In practice, at least one of the wrappers includes a wrapping substrate, and the flame-retardant composition containing one or more flame-retardant compounds can be applied as a coating on the wrapping substrate, or the wrapping substrate can be impregnated with the flame-retardant composition, or both. As a further alternative, the flame-retardant composition containing one or more flame-retardant compounds can be incorporated into the wrapper during the manufacture of the packaging material itself. For example, during the manufacture of paper-based or polymer-based packaging materials, the flame-retardant composition can be added to a pulp or polymer mixture during the wrapper manufacturing process. This can be advantageous in that it shortens the manufacturing process and allows for a more uniform distribution of the flame-retardant compounds throughout the packaging material.

[0040] The term "flame retardant compound" is used herein to describe a compound that, when added to or otherwise incorporated into a substrate, such as a paper or plastic compound, provides varying degrees of flammability protection to the substrate. In practice, flame retardant compounds may be activated by the presence of an ignition source and are adapted to prevent or delay the further development of ignition by a variety of different physical and chemical mechanisms.

[0041] The flame retardant composition may typically further comprise one of a plurality of non-flame retardant compounds, i.e., one or more compounds, such as solvents, excipients, fillers, etc., that do not actively contribute to providing flammability protection to the substrate, but that are used to facilitate the application of one or more flame retardant compounds onto and / or in the wrapper.

[0042] Some of the non-flame retardant compounds of the flame retardant composition, such as solvents, are volatile and can evaporate from the wrapper as it dries after the flame retardant composition is applied onto or into the wrapping substrate, or both. Thus, while these non-flame retardant compounds form part of the formulation of the flame retardant composition, they are no longer present, or can only be detected in trace amounts, in the wrapper of the aerosol-generating article according to the present invention.

[0043] To provide the flame retardant composition to a paper-based or polymer-based wrapper, the flame retardant composition may be added to the pulp or polymer mixture during the wrapper manufacturing process, or may be added to the wrapping substrate at a later stage by an application process based on size pressing, spraying, printing, coating, etc. The flame retardant composition may be applied, for example, as a layer, to one side of the wrapping substrate or to both sides of the wrapping substrate.

[0044] Many suitable flame retardant compounds are known. Some flame retardant compounds, such as mineral flame retardants, act primarily as additive flame retardants and do not chemically bond to the surrounding system. Most organohalogen compounds and organophosphate compounds also do not permanently react and adhere to the surroundings. Reactive flame retardant compounds, such as certain non-halogenated products, are reactive in that they are incorporated into the surrounding system without losing their flame retardant efficiency. This advantageously prevents these materials from being released into the environment.

[0045] The wrapping substrate of the wrapper surrounding the segment of material of the upstream element may be a paper wrapping substrate or a non-paper wrapping substrate. In a preferred embodiment, the wrapping substrate of the wrapper surrounding the segment of material of the upstream element comprises paper. Suitable paper wrapping substrates for use in certain embodiments of the present invention are known in the art and include, but are not limited to, cigarette paper and filter plug wrap. Suitable non-paper wrapping substrates for use in certain embodiments of the present invention are known in the art and include, but are not limited to, sheets of homogenized tobacco material and sheets of certain polymeric materials. In certain embodiments, the wrapping substrate may be formed from a laminate material comprising multiple layers.

[0046] In some embodiments, the wrapping substrate of the wrapper surrounding the segment of material of the upstream element may be non-porous, particularly the wrapping substrate of the first wrapper.

[0047] In some embodiments, the wrapping substrate of the first wrapper may have an air permeability of less than about 20 Coresta units.

[0048] The "Cholesta unit" is a unit of air permeability for a sheet material, corresponding to the flow of air (in cubic centimeters per minute) through one square centimeter of surface area of ​​the test material at a measured pressure of 1.00 kilopascals. The measured pressure is the pressure difference between the two sides of the test material being measured. Therefore, the unit corresponding to the Coresta unit is 1.00 kilopascals per cubic centimeter per minute per square centimeter (cm 3 min -1 cm -2 A suitable method for determining the air permeability of sheet materials for use in the present invention is described in ISO standard 2965:2009.

[0049] The air permeability in Coresta Units (CU) for the test specimen is calculated using the following formula: CU=[Q / A]x[1 / d]

[0050] where Q is the measured air flow through the specimen in cubic centimeters per minute, A is the surface area of ​​the specimen in square centimeters, and d is the measured pressure difference between the two surfaces of the specimen in kilopascals.

[0051] Wrappers having an air permeability of less than 20 Coresta units may also be described herein as "substantially impermeable." In preferred embodiments, the first wrapper has an air permeability of less than 20 Coresta units, more preferably less than 10 Coresta units, and even more preferably less than 5 Coresta units. In some particularly preferred embodiments, the air permeability of the substantially impermeable wrapper may have a lower limit of 1 Coresta unit.

[0052] By way of example, the wrapping substrate may have a basis weight of at least about 20 grams per square meter. Preferably, the wrapping substrate has a basis weight of at least about 25 grams per square meter. More preferably, the wrapping substrate has a basis weight of at least 30 grams per square meter. Even more preferably, the wrapping substrate has a basis weight of at least about 40 grams per square meter.

[0053] The wrapping substrate may have a basis weight of up to about 120 grams per square meter. Preferably, the wrapping substrate has a basis weight of about 110 grams per square meter or less. More preferably, the wrapping substrate has a basis weight of about 100 grams per square meter or less. Even more preferably, the wrapping substrate has a basis weight of about 90 grams per square meter or less.

[0054] In some embodiments, the wrapping substrate may have a basis weight of about 20 grams per square meter to about 120 grams per square meter, preferably about 25 grams per square meter to about 120 grams per square meter, more preferably about 30 grams per square meter to about 120 grams per square meter, and even more preferably about 40 grams per square meter to about 120 grams per square meter. In other embodiments, the wrapping substrate may have a basis weight of about 20 grams per square meter to about 110 grams per square meter, preferably about 25 grams per square meter to about 110 grams per square meter, more preferably about 30 grams per square meter to about 110 grams per square meter, and even more preferably about 40 grams per square meter to about 110 grams per square meter. In further embodiments, the wrapping substrate may have a basis weight of about 20 grams per square meter to about 100 grams per square meter, preferably about 25 grams per square meter to about 100 grams per square meter, more preferably about 30 grams per square meter to about 100 grams per square meter, and even more preferably about 40 grams per square meter to about 100 grams per square meter. In still other embodiments, the wrapping substrate may have a basis weight of about 20 grams per square meter to about 90 grams per square meter, preferably about 25 grams per square meter to about 90 grams per square meter, more preferably about 30 grams per square meter to about 90 grams per square meter, and even more preferably about 40 grams per square meter to about 90 grams per square meter.

[0055] For example, a first wrapper surrounding a segment of material of an upstream element may comprise a wrapping substrate having a basis weight of up to 100 grams per square meter.

[0056] For example, the second wrapper surrounding both the upstream element and the aerosol-generating element, i.e., the wrapper that joins the upstream element and the aerosol-generating element, may comprise a wrapping substrate having a basis weight of 20 grams per square meter to 60 grams per square meter, preferably 25 grams per square meter to 50 grams per square meter.

[0057] The lapping substrate may have a thickness of at least 20 micrometers. Preferably, the lapping substrate has a thickness of at least 25 micrometers. More preferably, the lapping substrate has a thickness of at least 30 micrometers.

[0058] The lapping substrate may have a thickness of 130 micrometers or less. Preferably, the lapping substrate has a thickness of 120 micrometers or less. More preferably, the lapping substrate has a thickness of 110 micrometers or less. Even more preferably, the lapping substrate has a thickness of 100 micrometers or less or 90 micrometers or less.

[0059] In some embodiments, the wrapping substrate has a thickness of 20 micrometers to 130 micrometers, preferably 20 micrometers to 120 micrometers, more preferably 20 micrometers to 110 micrometers, even more preferably 20 micrometers to 100 micrometers, or 20 micrometers to 90 micrometers. In other embodiments, the wrapping substrate has a thickness of 25 micrometers to 130 micrometers, preferably 25 micrometers to 120 micrometers, more preferably 25 micrometers to 110 micrometers, even more preferably 25 micrometers to 100 micrometers, or 25 micrometers to 90 micrometers. In further embodiments, the wrapping substrate has a thickness of 30 micrometers to 130 micrometers, preferably 30 micrometers to 120 micrometers, more preferably 30 micrometers to 110 micrometers, even more preferably 30 micrometers to 100 micrometers, or 30 micrometers to 90 micrometers.

[0060] For example, a first wrapper surrounding a segment of material of an upstream element may include a wrapping substrate having a thickness of up to 125 micrometers.

[0061] For example, the second wrapper surrounding both the upstream element and the aerosol-generation element, ie, the wrapper that joins the upstream element and the aerosol-generation element, may have a thickness of from 40 micrometers to 75 micrometers.

[0062] The wrapper surrounding at least the rod of aerosol-generating substrate has a total dry basis weight that is the sum of the basis weight of the wrapping substrate and the weight of the flame-retardant composition components present on the surface of the wrapping substrate, within the wrapping substrate, or both. The weight of the flame-retardant composition components present on or within the wrapper is the sum of the total weight of the flame-retardant compound(s) and the weight of any residual non-flame-retardant compounds. Within the context of the present invention, the weight of the flame-retardant composition components is also expressed in grams of component per square meter of wrapping substrate.

[0063] The ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper can be taken as an indication of the concentration of the flame retardant compounds in the wrapper.

[0064] In the aerosol-generating article according to the present invention, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper can be at least about 0.02. Preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is at least about 0.03. More preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is at least about 0.04. Even more preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is at least about 0.05.

[0065] Preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is about 0.20 or less. More preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is about 0.15 or less. Even more preferably, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper is about 0.10 or less.

[0066] In some embodiments, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper can be about 0.02 to about 0.20, preferably about 0.03 to about 0.20, more preferably about 0.04 to about 0.20, and even more preferably about 0.05 to about 0.20. In other embodiments, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper can be about 0.02 to about 0.15, preferably about 0.03 to about 0.15, more preferably about 0.04 to about 0.15, and even more preferably about 0.05 to about 0.15. In further embodiments, the ratio of the total weight of the flame retardant compounds to the total dry basis weight of the wrapper can be about 0.02 to about 0.10, preferably about 0.03 to about 0.10, more preferably about 0.04 to about 0.10, and even more preferably about 0.05 to about 0.10.

[0067] In the aerosol-generating article according to the present invention, the flame retardant composition is provided in a treated portion of the wrapper, meaning that the flame retardant composition is applied onto or in a corresponding portion of the wrapping substrate, or both. Thus, in the treated portion, the wrapper has a total dry basis weight greater than the dry basis weight of the wrapping substrate.

[0068] The treated portion of the wrapper may extend over at least about 10 percent of the outer surface area of ​​the segment of material of the upstream element surrounded by the wrapper. Preferably, the treated portion of the wrapper extends over at least about 20 percent of the outer surface area of ​​the segment of material of the upstream element surrounded by the wrapper. More preferably, the treated portion of the wrapper extends over at least about 40 percent of the outer surface area of ​​the segment of material of the upstream element. Even more preferably, the treated portion of the wrapper extends over at least about 60 percent of the outer surface area of ​​the segment of material of the upstream element. Most preferably, the treated portion of the wrapper extends over at least about 80 percent of the outer surface area of ​​the segment of material of the upstream element.

[0069] In particularly preferred embodiments, the treated portion of the wrapper extends over at least about 90 percent of the outer surface area of ​​the segment of material of the upstream element. Even more preferred, the treated portion of the wrapper extends over at least about 95 percent of the outer surface area of ​​the segment of material of the upstream element. Most preferred, the treated portion of the wrapper extends over substantially the entire outer surface area of ​​the segment of material of the upstream element.

[0070] The length of the treated region may be at least about 10 percent of the length of the segment of material of the upstream element. Preferably, the length of the treated region is at least about 20 percent of the length of the segment of material of the upstream element. More preferably, the length of the treated region is at least about 40 percent of the length of the segment of material of the upstream element. Even more preferably, the length of the treated region is at least about 60 percent of the length of the segment of material of the upstream element. Most preferably, the length of the treated region is at least about 80 percent of the length of the segment of material of the upstream element.

[0071] In particularly preferred embodiments, the length of the treated region is at least about 90 percent of the length of the segment of material of the upstream element. Even more preferred is that the length of the treated region is at least about 95 percent of the length of the segment of material of the upstream element. Most preferred is that the length of the treated region is substantially equal to the length of the segment of material of the upstream element.

[0072] At least about 10 grams of the flame retardant composition may be applied to the treated portion per square meter of the treated portion's surface area. Preferably, at least about 12 grams of the flame retardant composition is applied to the treated portion per square meter of the treated portion's surface area. More preferably, at least about 14 grams of the flame retardant composition is applied to the treated portion per square meter of the treated portion's surface area. Even more preferably, at least about 16 grams of the flame retardant composition is applied to the treated portion per square meter of the treated portion's surface area. In particularly preferred embodiments, at least about 18 grams, or at least about 20 grams of the flame retardant composition is applied to the treated portion per square meter of the treated portion's surface area.

[0073] Preferably, about 35 grams or less of the flame retardant composition is applied onto the treated portion per square meter of the surface area of ​​the treated portion. More preferably, about 30 grams or less of the flame retardant composition is applied onto the treated portion per square meter of the surface area of ​​the treated portion. Even more preferably, about 25 grams or less of the flame retardant composition is applied onto the treated portion per square meter of the surface area of ​​the treated portion.

[0074] In some embodiments, about 10 grams to about 35 grams of the flame retardant composition is applied to the treated portion per square meter of the surface area of ​​the treated portion. Preferably, about 12 grams to about 35 grams of the flame retardant composition is applied to the treated portion per square meter of the surface area of ​​the treated portion. More preferably, about 14 grams to about 35 grams of the flame retardant composition is applied to the treated portion per square meter of the surface area of ​​the treated portion. Even more preferably, about 16 grams to about 35 grams of the flame retardant composition is applied to the treated portion per square meter of the surface area of ​​the treated portion. In particularly preferred embodiments, about 18 grams to about 35 grams, or about 20 grams to about 35 grams of the flame retardant composition is applied to the treated portion per square meter of the surface area of ​​the treated portion.

[0075] In other embodiments, about 10 grams to about 30 grams of the flame retardant composition are applied to the treated portion per square meter of the surface area of ​​the treated portion. Preferably, about 12 grams to about 30 grams of the flame retardant composition are applied to the treated portion per square meter of the surface area of ​​the treated portion. More preferably, about 14 grams to about 30 grams of the flame retardant composition are applied to the treated portion per square meter of the surface area of ​​the treated portion. Even more preferably, about 16 grams to about 30 grams of the flame retardant composition are applied to the treated portion per square meter of the surface area of ​​the treated portion. In particularly preferred embodiments, about 18 grams to about 30 grams, or about 20 grams to about 30 grams of the flame retardant composition are applied to the treated portion per square meter of the surface area of ​​the treated portion.

[0076] In further embodiments, about 10 grams to about 25 grams of the flame retardant composition are applied onto the treated portion per square meter of the surface area of ​​the treated portion. Preferably, about 12 grams to about 25 grams of the flame retardant composition are applied onto the treated portion per square meter of the surface area of ​​the treated portion. More preferably, about 14 grams to about 25 grams of the flame retardant composition are applied onto the treated portion per square meter of the surface area of ​​the treated portion. Even more preferably, about 16 grams to about 25 grams of the flame retardant composition are applied onto the treated portion per square meter of the surface area of ​​the treated portion. In particularly preferred embodiments, about 18 grams to about 25 grams, or about 20 grams to about 25 grams of the flame retardant composition are applied onto the treated portion per square meter of the surface area of ​​the treated portion.

[0077] The treated portion of the wrapper may contain at least about 0.1 grams of flame retardant compound per square meter of surface area of ​​the treated portion. Preferably, the treated portion of the wrapper contains at least about 0.5 grams of flame retardant compound per square meter of surface area of ​​the treated portion. More preferably, the treated portion of the wrapper contains at least about 1.0 grams of flame retardant compound per square meter of surface area of ​​the treated portion. Even more preferably, the treated portion of the wrapper contains at least about 2.0 grams of flame retardant compound per square meter of surface area of ​​the treated portion. In particularly preferred embodiments, the treated portion of the wrapper contains at least about 3.0 grams of flame retardant compound per square meter of surface area of ​​the treated portion, or at least about 4.0 grams of flame retardant compound per square meter of surface area of ​​the treated portion, or at least about 5.0 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0078] In some embodiments, the treated portion of the wrapper comprises at least about 10 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0079] Preferably, the treated portion of the wrapper contains no more than about 100 grams of flame retardant compound per square meter of surface area of ​​the treated portion. More preferably, the treated portion of the wrapper contains no more than about 50 grams of flame retardant compound per square meter of surface area of ​​the treated portion. Even more preferably, the treated portion of the wrapper contains no more than about 25 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0080] In some embodiments, the treated portion of the wrapper comprises from about 0.5 grams to about 12 grams of flame retardant compound per square meter of surface area of ​​the treated portion, preferably from about 1.0 grams to about 12 grams of flame retardant compound per square meter of surface area of ​​the treated portion, more preferably from about 2.0 grams to about 12 grams of flame retardant compound per square meter of surface area of ​​the treated portion, and even more preferably from about 3.0 grams to about 12 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0081] In other embodiments, the treated portion of the wrapper comprises from about 0.5 grams to about 10 grams of flame retardant compound per square meter of surface area of ​​the treated portion, preferably from about 1.0 grams to about 10 grams of flame retardant compound per square meter of surface area of ​​the treated portion, more preferably from about 2.0 grams to about 10 grams of flame retardant compound per square meter of surface area of ​​the treated portion, and even more preferably from about 3.0 grams to about 120 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0082] In a further embodiment, the treated portion of the wrapper comprises from about 0.5 grams to about 8 grams of flame retardant compound per square meter of surface area of ​​the treated portion, preferably from about 1.0 grams to about 12 grams of flame retardant compound per square meter of surface area of ​​the treated portion, more preferably from about 2.0 grams to about 8 grams of flame retardant compound per square meter of surface area of ​​the treated portion, and even more preferably from about 3.0 grams to about 8 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0083] In some particularly preferred embodiments, the treated portion of the wrapper comprises from about 10 grams to about 100 grams of flame retardant compound per square meter of surface area of ​​the treated portion, preferably from about 10 grams to about 50 grams of flame retardant compound per square meter of surface area of ​​the treated portion, and more preferably from about 10 grams to about 25 grams of flame retardant compound per square meter of surface area of ​​the treated portion.

[0084] In the aerosol-generating article according to the present invention, the content of the one or more flame-retardant compounds in the treated portion is preferably such that the aerosol-generating article does not ignite when heated using a resistance heating coil at 500° C. for at least 5 seconds, preferably 30 seconds. The term "does not ignite" as used herein means, in particular, that combustion of the wrapper surrounding the aerosol-generating substrate does not commence and no flame is detectable.

[0085] Preferably, an aerosol-generating article according to the present invention includes a pre-ignition step using a resistive heating coil and does not ignite when submitted to the Health Canada Intense Method under a puff regime of one puff of 55 milliliters and 2 seconds duration every 30 seconds with 100 percent of the ventilation zone (if present) on the aerosol-generating article blocked. ISO 3308:2000 (Routine analytical cigarette smoking machine - definitions and standard conditions) provides further details regarding "smoking" parameters and standard test conditions.

[0086] Many suitable flame retardant compounds will be known to those skilled in the art. In particular, several flame retardant compounds and formulations suitable for the treatment of cellulosic materials are known and disclosed and may find use in the manufacture of wrappers for aerosol-generating articles according to the present invention.

[0087] In some embodiments, the flame retardant composition comprises a polymer and a mixed salt based on at least one mono-, di-, and / or tricarboxylic acid, at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid, and a hydroxide or salt of an alkali or alkaline earth metal, wherein the at least one mono-, di-, and / or tricarboxylic acid and the hydroxide or salt forms a carboxylate salt, and the at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid and the hydroxide or salt forms a phosphate salt.

[0088] Preferably, in such embodiments, the flame retardant composition further comprises a carbonate of an alkali or alkaline earth metal.

[0089] In another embodiment, the flame retardant composition comprises at least one C 10 The cellulose may be modified with any of the above fatty acids, such as tall oil fatty acid (TOFA), phosphorylated linseed oil, and phosphorylated corn oil. Preferably, the cellulose may be modified with at least one C 10 The fatty acids are selected from the group consisting of capric acid, myristic acid, palmitic acid, and combinations thereof.

[0090] In aerosol-generating articles according to the invention, it is preferred that neither the first nor the second wrapper contain metal, which may advantageously enhance the environmental compatibility of aerosol-generating articles according to the invention, as metal components do not need to be separated from the rest of the article upon disposal.

[0091] In some embodiments, the upstream element is disposed immediately upstream of the aerosol-generating element. Preferably, the upstream element abuts the upstream end of the aerosol-generating article. Thus, the upstream element may extend from the upstream end of the aerosol-generating element to the upstream or distal end of the aerosol-generating article.

[0092] In other embodiments, the aerosol-generating article comprises one or more intermediate components disposed between the upstream element and the aerosol-generating element. Preferably, the upstream element abuts the upstream end of one such intermediate component disposed immediately downstream of the upstream element. Thus, the upstream element may extend from the upstream end of the intermediate component to the upstream or distal end of the aerosol-generating article.

[0093] The aerosol-generating article may include an air inlet at the upstream end of the aerosol-generating article, which may be provided through the upstream element, such that air entering through the air inlet may pass through the aerosol-generating element to generate mainstream aerosol.

[0094] The upstream element may advantageously prevent direct physical contact with the upstream end of the aerosol-generating element. In particular, when the aerosol-generating element comprises a susceptor element embedded within the aerosol-generating substrate, as described in more detail below, the upstream element may prevent direct physical contact with the upstream end of the susceptor element. This helps to prevent displacement or deformation of the susceptor element during handling or transport of the aerosol-generating article. This, in turn, helps to fix the shape and position of the susceptor element. Furthermore, the presence of the upstream element may help to prevent any loss of the aerosol-generating substrate, which may be advantageous, for example, when the aerosol-generating substrate contains particulate material, such as particulate plant material.

[0095] The upstream element may also provide an improved appearance to the upstream end of the aerosol-generating article. Additionally, if desired, the upstream element may be used to provide information about the aerosol-generating article, such as the brand, flavor, content, or details of the aerosol-generating device in which the article is intended to be used.

[0096] The segment of material of the upstream element may be in the form of a porous plug element. The porous plug element may have a porosity of at least about 50 percent along the longitudinal axis of the aerosol-generating article. More preferably, the porous plug element has a porosity of between about 50 percent and about 90 percent along the longitudinal axis. The porosity of the porous plug element along the longitudinal axis is determined by the ratio of the cross-sectional area of ​​the material forming the porous plug element to the internal cross-sectional area of ​​the aerosol-generating article at the location of the porous plug element.

[0097] The porous plug element may be made of a porous material or may include a plurality of openings, which may be achieved, for example, by laser drilling. The plurality of openings is preferably uniformly distributed across the cross section of the porous plug element.

[0098] The porosity or permeability of the upstream element may be advantageously varied to provide a desired overall resistance to withdrawal of the aerosol-generating article.

[0099] In alternative embodiments, the upstream element may be formed from a material that is impermeable to air. In such embodiments, the aerosol-generating article may be configured to allow air to flow into the aerosol-generating element via suitable venting means provided in the wrapper.

[0100] The segment of material of the upstream element may comprise any suitable material for use in an aerosol-generating article. For example, the segment of material of the upstream element may include a filter material, a ceramic, a polymeric material, cellulose acetate, paper, cardboard, a zeolite, or an aerosol-generating substrate. Preferably, the segment of material comprises a plug of cellulose acetate. In some embodiments, the segment of material of the upstream element is made substantially of paper.

[0101] The upstream element preferably has a diameter approximately equal to the diameter of the aerosol-generating article.

[0102] Preferably, the upstream element has an outer diameter of at least about 5 millimeters. More preferably, the upstream element has an outer diameter of at least about 6 millimeters. Even more preferably, the upstream element has an outer diameter of at least about 7 millimeters.

[0103] Preferably, the upstream element has an outer diameter of about 12 millimeters or less. More preferably, the upstream element has an outer diameter of about 10 millimeters or less. Even more preferably, the upstream element has an outer diameter of about 8 millimeters or less.

[0104] In some embodiments, the upstream element has an outer diameter of about 5 millimeters to about 12 millimeters, preferably about 5 millimeters to about 10 millimeters, and more preferably about 5 millimeters to about 8 millimeters. In other embodiments, the upstream element has an outer diameter of about 6 millimeters to about 12 millimeters, preferably about 6 millimeters to about 10 millimeters, and more preferably about 6 millimeters to about 8 millimeters. In further embodiments, the upstream element has an outer diameter of about 7 millimeters to about 12 millimeters, preferably about 7 millimeters to about 10 millimeters, and more preferably about 7 millimeters to about 8 millimeters.

[0105] The upstream element can have a length of at least 1 millimeter. For example, the upstream element can have a length of at least about 2 millimeters, preferably at least about 4 millimeters, and more preferably at least about 6 millimeters.

[0106] The upstream element can have a length of about 25 millimeters or less. For example, the upstream element can have a length of about 20 millimeters or less, preferably about 15 millimeters or less, more preferably about 12 millimeters or less, and even more preferably about 10 millimeters or less. In particularly preferred embodiments, the upstream element has a length of about millimeters or less.

[0107] In some embodiments, the upstream element has a length of about 1 millimeter to about 20 millimeters, preferably about 1 millimeter to about 15 millimeters, more preferably about 1 millimeter to about 12 millimeters, even more preferably about 1 millimeter to about 10 millimeters, and most preferably about 1 millimeter to about 8 millimeters.

[0108] In other embodiments, the upstream element has a length of about 2 millimeters to about 20 millimeters, preferably about 2 millimeters to about 15 millimeters, more preferably about 2 millimeters to about 12 millimeters, even more preferably about 2 millimeters to about 10 millimeters, and most preferably about 2 millimeters to about 8 millimeters.

[0109] In a further embodiment, the upstream element has a length of about 4 millimeters to about 20 millimeters, preferably about 4 millimeters to about 15 millimeters, more preferably about 4 millimeters to about 12 millimeters, even more preferably about 4 millimeters to about 10 millimeters, and most preferably about 4 millimeters to about 8 millimeters.

[0110] In still other embodiments, the upstream element has a length of about 6 millimeters to about 20 millimeters, preferably about 6 millimeters to about 15 millimeters, more preferably about 6 millimeters to about 12 millimeters, even more preferably about 6 millimeters to about 10 millimeters, and most preferably about 6 millimeters to about 8 millimeters.

[0111] The length of the upstream element may be advantageously varied to adjust the overall length of the aerosol-generating article. For example, if it is desired to reduce the length of one of the other components of the aerosol-generating article, the length of the upstream element may be increased to maintain the same overall length of the article. Furthermore, by adjusting the length of the upstream element, it may be possible to control how far the aerosol-generating article protrudes from the heating cavity of the aerosol-generating device when the aerosol-generating article is inserted into the heating cavity during use.

[0112] The segment of material of the upstream element preferably has a substantially homogeneous structure. For example, the segment of material of the upstream element may be substantially homogeneous in texture and appearance. The segment of material of the upstream element may, for example, have a continuous regular surface over its entire cross section. The segment of material of the upstream element may, for example, not have a discernible symmetry.

[0113] The segment of material of the upstream element may be in the form of a tubular body. Accordingly, the segment of material of the upstream element may internally define a cavity extending from the upstream end of the tubular body to the downstream end of the tubular body. The tubular body may also include a folded end portion forming a first end wall at the first upstream end of the tubular body. The first end wall may define an opening that allows airflow between the cavity and the exterior of the tubular body. Preferably, air may flow from the cavity through the opening into the aerosol-generating element.

[0114] The tubular body may include a second end wall at the downstream end of the tubular body. This second end wall may be formed by folding an end portion of the tubular body at the downstream end of the tubular body. The second end wall may define an opening that may allow airflow between the cavity and the exterior of the tubular body. In the case of the second end wall, the opening may be configured to allow air to flow from the exterior of the aerosol-generating article through the opening and into the cavity. Thus, the opening may provide a conduit through which air may be drawn into the aerosol-generating article and through the aerosol-generating substrate.

[0115] In certain embodiments, the segment of material comprises a spirally wound sheet defining a plurality of longitudinally extending channels.

[0116] Inclusion of such a segment of material in the upstream element of an aerosol-generating article according to the present invention can advantageously reduce or prevent detachment of aerosol-generating material from the aerosol-generating element during storage, transport, and use of the aerosol-generating article, while still providing an acceptable RTD. Inclusion of such a segment of material in the upstream element can advantageously reduce or prevent aerosol-generating material that has detached from the aerosol-generating element from falling into the cavity of the aerosol generating device during use of the aerosol-generating article. Inclusion of such a segment of material in the upstream element can advantageously limit or prevent longitudinal movement of the aerosol-generating element during storage, transport, and use of the aerosol-generating article.

[0117] Preferably, the segment of material comprises a tubular portion defining an interior region of the upstream element, and the spiral sheet is disposed within the tubular portion such that a plurality of longitudinally extending channels are defined within the interior region.

[0118] The spiral sheet divides the interior region of the upstream element into multiple longitudinally extending channels along which air can be drawn through the upstream element. The spiral sheet can thereby reduce the cross-sectional area of ​​void space within the upstream element into which the aerosol-generating material within the aerosol-generating element can escape, while still providing an acceptable RTD. This can be particularly advantageous when the aerosol-generating substrate within the aerosol-generating element includes multiple strips, pellets, or granules of aerosol-generating material.

[0119] The spirally wound sheet may have a basis weight of up to 200 grams per square meter. Preferably, the spirally wound sheet has a basis weight of 150 grams per square meter or less. More preferably, the spirally wound sheet has a basis weight of 100 grams per square meter or less.

[0120] The inclusion of a spirally wound sheet having a basis weight of about 100 grams per square meter or less may allow the spirally wound sheet to have a larger cross-sectional area while maintaining a suitable total weight of the upstream element, thereby dividing the interior region of the upstream element into more longitudinally extending channels while maintaining a suitable total weight of the upstream element.

[0121] The spiral sheet can advantageously act as a barrier to prevent or limit longitudinal movement of the aerosol-generating substrate during storage, transport, and use of the aerosol-generating article.

[0122] Therefore, providing an aerosol-generating article comprising an upstream element having the above-mentioned characteristics may improve the quality and consistency of the aerosol delivered to the user compared to known heated tobacco products and may enable optimal functioning of the aerosol generating device of the aerosol generation system according to the second aspect of the present invention.

[0123] The spirally wound sheet comprises a plurality of turns. Preferably, the spirally wound sheet comprises a plurality of non-concentric turns.

[0124] The spirally wound sheet defines a plurality of longitudinally extending channels in the interior region of the upstream element, and may be one or more of crimped, folded, gathered, and pleated to define the plurality of longitudinally extending channels.

[0125] As used herein with respect to the present invention, the term "crimped" refers to a spirally wound sheet having a plurality of substantially parallel ridges or corrugations. Preferably, when the spirally wound sheet is crimped, the substantially parallel ridges or corrugations of the spirally wound sheet extend in the longitudinal direction of the aerosol-generating article.

[0126] As used herein with respect to the present invention, the term "assembled" means that the sheet is compressed or contracted substantially transversely to the longitudinal axis of the aerosol-generating article.

[0127] The spiral sheet is preferably crimped, which may advantageously reduce variations in cross-sectional area of ​​the plurality of longitudinally extending channels defined by the spiral sheet within the interior region of the upstream element.

[0128] The inclusion of a crimped spiral sheet within the upstream element may advantageously avoid or reduce the presence of longitudinally extending channels with very large cross-sectional areas in the interior region of the upstream element, which may adversely affect the ability of the upstream element to prevent or restrict the upstream migration of aerosol-generating material from the aerosol-generating substrate.

[0129] The inclusion of a crimped spiral sheet in the upstream element can advantageously avoid or reduce the presence of longitudinally extending channels with very small cross-sectional areas in the interior region of the upstream element, which can increase the RTD of the upstream element beyond acceptable or desirable levels.

[0130] When the spirally coiled sheet is crimped, adjacent ridges or corrugations of the spirally coiled sheet may be spaced apart from one another by no more than about 1.2 millimeters, no more than about 1 millimeter, or no more than about 0.8 millimeters. For example, adjacent ridges or corrugations may be spaced apart from one another by no more than about 0.5 millimeters. The spacing between adjacent ridges or corrugations may be selected based on the desired size of the plurality of longitudinally extending channels.

[0131] The spirally wound sheet may be crimped and then collected, i.e., the spirally wound sheet may be a collection of crimped sheets.

[0132] Generally, the upstream element material segment may have a weight of at least 10 milligrams, preferably at least 20 milligrams, and more preferably at least 30 milligrams. The upstream element material segment may have a weight of 100 milligrams or less, preferably 75 milligrams or less, and more preferably 50 milligrams or less. In some embodiments, the upstream element material segment has a weight of 10 milligrams to 100 milligrams, preferably 20 milligrams to 100 milligrams, and more preferably 30 milligrams to 100 milligrams. In other embodiments, the upstream element material segment has a weight of 10 milligrams to 75 milligrams, preferably 20 milligrams to 75 milligrams, and more preferably 30 milligrams to 75 milligrams. In further embodiments, the upstream element material segment has a weight of 10 milligrams to 50 milligrams, preferably 20 milligrams to 50 milligrams, and more preferably 30 milligrams to 50 milligrams. In some preferred embodiments, the upstream element material segment may have a weight of approximately 40 milligrams.

[0133] The RTD of the segment of material of the upstream element may be at least about 1 millimeter H2O, at least about 2 millimeters H2O, or at least about 4 millimeters H2O.

[0134] The RTD of the segment of material of the upstream element may be about 10 millimeters H2O or less, about 8 millimeters H2O or less, or about 6 millimeters H2O or less.

[0135] The RTD of the segment of material of the upstream element may be from about 1 millimeter HO to about 10 millimeters HO, from about 1 millimeter HO to about 8 millimeters HO, or from about 1 millimeter HO to about 6 millimeters HO.

[0136] The RTD of the segment of material of the upstream element may be from about 2 millimeters HO to about 10 millimeters HO, from about 2 millimeters HO to about 8 millimeters HO, or from about 2 millimeters HO to about 8 millimeters HO.

[0137] The RTD of the segment of material of the upstream element may be from about 4 millimeters HO to about 10 millimeters HO, from about 4 millimeters HO to about 8 millimeters HO, or from about 4 millimeters HO to about 6 millimeters HO.

[0138] In some preferred embodiments, the RTD of the segment of material in the upstream element is about 5 millimeters H2O or 5.5 millimeters H2O.

[0139] In an aerosol-generating article according to the invention, the aforementioned upstream element is provided upstream of the aerosol-generating element and comprises a rod of aerosol-generating substrate surrounded by a rod plug wrap, as described above. As used herein in relation to the present invention, the term "rod" is used to mean a generally cylindrical element having a substantially circular, oval or elliptical cross-section.

[0140] The aerosol-generating element may have a length of at least about 8 millimeters, at least about 9 millimeters, or at least about 10 millimeters.

[0141] The aerosol-generating element may have a length of about 16 millimeters or less, about 15 millimeters or less, or about 14 millimeters or less.

[0142] The aerosol-generating element may have a length of about 8 millimeters to about 16 millimeters, about 8 millimeters to about 15 millimeters, or about 8 millimeters to about 14 millimeters.

[0143] The aerosol-generating element may have a length of about 9 millimeters to about 16 millimeters, about 9 millimeters to about 15 millimeters, or about 9 millimeters to about 14 millimeters.

[0144] The aerosol-generating element may have a length of about 10 millimeters to about 16 millimeters, about 10 millimeters to about 15 millimeters, or about 10 millimeters to about 14 millimeters.

[0145] For example, the aerosol-generating element may have a length of about 12 millimeters.

[0146] The ratio of the length of the aerosol-generating element to the overall length of the aerosol-generating article may be at least about 0.10, at least about 0.15, or at least about 0.20.

[0147] The ratio of the length of the aerosol-generating element to the overall length of the aerosol-generating article may be about 0.40 or less, about 0.35 or less, or about 0.3 or less.

[0148] The ratio of the length of the aerosol-generating element to the overall length of the aerosol-generating article may be from about 0.10 to about 0.40, from about 0.10 to about 0.35, or from about 0.10 to about 0.30.

[0149] The ratio of the length of the aerosol-generating element to the overall length of the aerosol-generating article may be from about 0.15 to about 0.40, from about 0.15 to about 0.35, or from about 0.15 to about 0.30.

[0150] The ratio of the length of the aerosol-generating element to the overall length of the aerosol-generating article may be from about 0.20 to about 0.40, from about 0.20 to about 0.35, or from about 0.20 to about 0.30.

[0151] Preferably, the aerosol-generating element has a substantially circular cross-section.

[0152] The aerosol-generating element may have an outer diameter of at least about 5 millimeters, at least about 6 millimeters, or at least about 7 millimeters.

[0153] The aerosol-generating element may have an outer diameter of 12 millimeters or less, about 10 millimeters or less, or about 8 millimeters or less.

[0154] The aerosol-generating element may have an outer diameter of about 5 millimeters to about 12 millimeters, about 5 millimeters to about 10 millimeters, or about 5 millimeters to about 8 millimeters.

[0155] The aerosol-generating element may have an outer diameter of about 6 millimeters to about 12 millimeters, about 6 millimeters to about 10 millimeters, or about 6 millimeters to about 8 millimeters.

[0156] The aerosol-generating element may have an outer diameter of about 7 millimeters to about 12 millimeters, about 7 millimeters to about 10 millimeters, or about 7 millimeters to about 8 millimeters.

[0157] For example, the aerosol-generating element may have an outer diameter of about 7.1 millimeters.

[0158] The aerosol-generating substrate may have a density of at least about 150 milligrams per cubic centimeter, at least about 175 milligrams per cubic centimeter, at least about 200 milligrams per cubic centimeter, or at least about 250 milligrams per cubic centimeter.

[0159] The aerosol-generating substrate may have a density of about 500 milligrams per cubic centimeter or less, about 450 milligrams per cubic centimeter or less, about 400 milligrams per cubic centimeter or less, or about 350 milligrams per cubic centimeter or less.

[0160] The aerosol-generating substrate may have a density of from about 150 milligrams / cubic centimeter to about 500 milligrams / cubic centimeter, from about 150 milligrams / cubic centimeter to about 450 milligrams / cubic centimeter, from about 150 milligrams / cubic centimeter to about 400 milligrams / cubic centimeter, or from about 150 milligrams / cubic centimeter to about 350 milligrams / cubic centimeter.

[0161] The aerosol-generating substrate may have a density of from about 175 milligrams / cubic centimeter to about 500 milligrams / cubic centimeter, from about 175 milligrams / cubic centimeter to about 450 milligrams / cubic centimeter, from about 175 milligrams / cubic centimeter to about 400 milligrams / cubic centimeter, or from about 175 milligrams / cubic centimeter to about 350 milligrams / cubic centimeter.

[0162] The aerosol-generating substrate may have a density of from about 200 milligrams / cubic centimeter to about 500 milligrams / cubic centimeter, from about 200 milligrams / cubic centimeter to about 450 milligrams / cubic centimeter, from about 200 milligrams / cubic centimeter to about 400 milligrams / cubic centimeter, or from about 200 milligrams / cubic centimeter to about 350 milligrams / cubic centimeter.

[0163] The aerosol-generating substrate may have a density of from about 250 milligrams / cubic centimeter to about 500 milligrams / cubic centimeter, from about 250 milligrams / cubic centimeter to about 450 milligrams / cubic centimeter, from about 250 milligrams / cubic centimeter to about 400 milligrams / cubic centimeter, or from about 250 milligrams / cubic centimeter to about 350 milligrams / cubic centimeter.

[0164] For example, the aerosol-generating substrate may have a density of about 300 milligrams per cubic centimeter.

[0165] The RTD of the rod of the aerosol-generating substrate may be at least about 4 millimeters H2O, at least about 5 millimeters H2O, or at least about 6 millimeters H2O.

[0166] The RTD of the rod of the aerosol-generating substrate may be about 10 millimeters H2O or less, about 9 millimeters H2O or less, or about 8 millimeters H2O or less.

[0167] The RTD of the rod of the aerosol-generating substrate may be from about 4 millimeters H2O to about 10 millimeters H2O, from about 4 millimeters H2O to about 9 millimeters H2O, or from about 4 millimeters H2O to about 8 millimeters H2O.

[0168] The RTD of the rod of the aerosol-generating substrate may be from about 5 millimeters H2O to about 10 millimeters H2O, from about 5 millimeters H2O to about 9 millimeters H2O, or from about 5 millimeters H2O to about 8 millimeters H2O.

[0169] The RTD of the rod of the aerosol-generating substrate may be from about 6 millimeters H2O to about 10 millimeters H2O, from about 6 millimeters H2O to about 9 millimeters H2O, or from about 6 millimeters H2O to about 8 millimeters H2O.

[0170] The aerosol-generating substrate may be a solid aerosol-generating substrate.

[0171] The aerosol-generating substrate preferably comprises an aerosol-forming material.

[0172] The aerosol former can be any suitable known compound or mixture of compounds that promotes the formation of a dense, stable aerosol during use. The aerosol former can promote the aerosol to be substantially resistant to thermal decomposition at temperatures typically encountered during use of the aerosol-generating article. Suitable aerosol formers include, for example, polyhydric alcohols (e.g., triethylene glycol, 1,3-butanediol, propylene glycol, glycerin, etc.), esters of polyhydric alcohols (e.g., glycerol mono-, di-, or triacetate, etc.), aliphatic esters of mono-, di-, or polycarboxylic acids (e.g., dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.), and combinations thereof.

[0173] The aerosol former preferably comprises one or more of glycerin and propylene glycol. The aerosol former may consist of glycerin, or propylene glycol, or a combination of glycerin and propylene glycol.

[0174] The aerosol-generating substrate may comprise at least about 5 weight percent, at least about 10 weight percent, or at least about 12 weight percent aerosol former, based on the dry weight of the aerosol-generating substrate.

[0175] The aerosol-generating substrate may comprise about 30 weight percent or less, about 25 weight percent or less, or about 20 weight percent or less of aerosol formers, based on the dry weight of the aerosol-generating substrate.

[0176] The aerosol-generating substrate may comprise from about 5 weight percent to about 30 weight percent, from about 5 weight percent to about 25 weight percent, or from about 5 weight percent to about 20 weight percent of aerosol-forming material, based on the dry weight of the aerosol-generating substrate.

[0177] The aerosol-generating substrate may comprise from about 10 weight percent to about 30 weight percent, from about 10 weight percent to about 25 weight percent, or from about 10 weight percent to about 20 weight percent aerosol former, based on the dry weight of the aerosol-generating substrate.

[0178] The aerosol-generating substrate may comprise from about 12 weight percent to about 30 weight percent, from about 12 weight percent to about 25 weight percent, or from about 12 weight percent to about 20 weight percent aerosol former, based on the dry weight of the aerosol-generating substrate.

[0179] The aerosol-generating substrate may comprise a plurality of strips of tobacco material.The aerosol-generating substrate may comprise a plurality of strips of homogenized tobacco material.

[0180] As used herein with respect to the present invention, the term "strip" means an element having a length that is substantially greater than its width and thickness.

[0181] As used herein with respect to the present invention, the term "homogenized tobacco material" is used to describe a material formed by agglomerating particulate tobacco material.

[0182] The strips of homogenized tobacco material may be formed from a sheet of homogenized tobacco material, for example, by cutting or chopping. The strips of homogenized tobacco material may also be formed by other methods, for example, by extrusion.

[0183] The strips of tobacco material may have a width of at least about 0.3 millimeters, at least about 0.5 millimeters, or at least about 0.6 millimeters.

[0184] The strips of tobacco material may have a width of about 2 millimeters or less, about 1.2 millimeters or less, or less than about 0.9 millimeters.

[0185] The strips of tobacco material may have a width of about 0.3 millimeters to about 2 millimeters, about 0.3 millimeters to about 1.2 millimeters, or about 0.3 millimeters to about 0.9 millimeters.

[0186] The strips of tobacco material may have a width of about 0.5 millimeters to about 2 millimeters, about 0.5 millimeters to about 1.2 millimeters, or about 0.5 millimeters to about 0.9 millimeters.

[0187] The strips of tobacco material may have a width of about 0.6 millimeters to about 2 millimeters, about 0.6 millimeters to about 1.2 millimeters, or about 0.6 millimeters to about 0.9 millimeters.

[0188] The strips of tobacco material may have a length of at least about 10 millimeters.

[0189] The strips of tobacco material may have a length of about 40 millimeters or less.

[0190] The strips of tobacco material may have a length of from about 10 millimeters to about 40 millimeters.

[0191] On a dry weight basis, at least about 20 weight percent of the plurality of strips of tobacco material may extend along the entire length of the aerosol-generating substrate.On a dry weight basis, at least about 20 weight percent of the plurality of strips of tobacco material may have a length substantially the same as the length of the aerosol-generating substrate.

[0192] On a dry weight basis, about 60 percent by weight or less of the plurality of strips of tobacco material may extend along the entire length of the aerosol-generating substrate.On a dry weight basis, about 60 percent by weight or less of the plurality of strips of tobacco material may have a length substantially the same as the length of the aerosol-generating substrate.

[0193] Between about 20 percent and 60 percent by weight of the plurality of strips of tobacco material, on a dry weight basis, may extend along the entire length of the aerosol-generating substrate. Between about 20 percent and 60 percent by weight of the plurality of strips of tobacco material, on a dry weight basis, may have a length that is substantially the same as the length of the aerosol-generating substrate.

[0194] The size of the aerosol-generating material of an aerosol-generating substrate, such as multiple strips of tobacco material, can play a role in the distribution of heat within the aerosol-generating substrate. The size of the aerosol-generating material can also play a role in the resistance to withdrawal of the article. Additionally, the size of the aerosol-generating material can affect the ability of the upstream element to prevent or restrict migration of the aerosol-generating material into the longitudinally extending channels of the upstream element. The size of the aerosol-generating material can also affect the ability of the upstream element to prevent or restrict upstream migration of the aerosol-generating material along the longitudinally extending channels and out of the upstream element.

[0195] The aerosol-generating substrate may comprise a plurality of pellets or granules of tobacco material.The aerosol-generating substrate may comprise a plurality of pellets or granules of homogenized tobacco material.

[0196] At least about 60 percent by weight of the plurality of pellets or granules may have a largest dimension greater than about 1 millimeter, at least about 70 percent by weight of the plurality of pellets or granules may have a largest dimension greater than about 1 millimeter, or at least about 80 percent by weight of the plurality of pellets or granules may have a largest dimension greater than about 1 millimeter.

[0197] If the homogenized plant material is in the form of a plurality of pellets or granules, at least about 70 percent by weight of the plurality of pellets or granules may have a maximum dimension greater than about 0.5 millimeters, at least about 80 percent by weight of the plurality of pellets or granules may have a maximum dimension greater than about 0.5 millimeters, or at least about 90 percent by weight of the plurality of pellets or granules may have a maximum dimension greater than about 0.5 millimeters.

[0198] For example, at least about 80 weight percent of the plurality of pellets or granules may have a maximum dimension greater than about 1 millimeter, and at least about 90 weight percent of the plurality of pellets or granules may have a maximum dimension greater than about 0.5 millimeters.

[0199] The aerosol-generating substrate may comprise one or more sheets of tobacco material.

[0200] The aerosol-generating substrate may comprise one or more sheets of homogenized tobacco material.

[0201] Each individual piece or sheet of tobacco material can have a thickness of at least about 100 micrometers, at least about 150 micrometers, or at least about 300 micrometers.

[0202] As used herein with respect to the present invention, individual thickness refers to the thickness of an individual sheet of tobacco material, and combined thickness refers to the total thickness of all sheets of tobacco material that make up the aerosol-generating substrate. For example, if the aerosol-generating substrate is formed from two individual sheets of tobacco material, the combined thickness is the sum of the thicknesses of the two individual sheets of tobacco material, or the measured thickness of the two sheets of tobacco material when the two sheets of tobacco material are laminated to the aerosol-generating substrate.

[0203] The one or more sheets of tobacco material may each individually have a thickness of not more than about 600 micrometers, not more than about 300 micrometers, or not more than about 250 micrometers.

[0204] The one or more sheets of tobacco material can each individually have a thickness of from about 100 micrometers to about 600 micrometers, from about 100 micrometers to about 300 micrometers, or from about 100 micrometers to about 250 micrometers.

[0205] The one or more sheets of tobacco material can each individually have a thickness of from about 150 micrometers to about 600 micrometers, from about 150 micrometers to about 300 micrometers, or from about 150 micrometers to about 250 micrometers.

[0206] The one or more sheets of tobacco material can each individually have a thickness of from about 250 micrometers to about 600 micrometers, from about 250 micrometers to about 300 micrometers, or from about 250 micrometers to about 250 micrometers.

[0207] The one or more sheets of tobacco material may each individually have a length that is substantially the same as the length of the aerosol-generating substrate.

[0208] The one or more sheets of tobacco material may be subjected to one or more of the following processes: crimping, folding, gathering, and pleating.

[0209] Crimping, folding, gathering, or pleating one or more sheets of tobacco material may cause the one or more sheets of tobacco material to split to form strips of tobacco material. For example, one or more sheets of tobacco material may be crimped to an extent that the integrity of the one or more sheets of tobacco material is broken at a plurality of parallel ridges or corrugations, causing the material to separate and forming strips of tobacco material.

[0210] The aerosol-generating substrate may comprise a gel composition comprising nicotine, at least one gelling agent, and an aerosol former. Preferably, the gel composition is substantially tobacco-free.

[0211] The preferred weight ranges of nicotine in the gel composition are the same as those defined above in connection with the aerosol-generating film.

[0212] The gel composition preferably comprises at least 50 weight percent aerosol former, more preferably at least 60 weight percent, more preferably at least 70 weight percent aerosol former, on a dry weight basis. The gel composition may comprise up to 80 weight percent aerosol former. The aerosol former in the gel composition is preferably glycerol.

[0213] The gel composition preferably includes at least one gelling agent in a total amount ranging from about 0.4 weight percent to about 10 weight percent, or from about 0.5 weight percent to about 8 weight percent, or from about 1 weight percent to about 6 weight percent, or from about 2 weight percent to about 4 weight percent, or from about 2 weight percent to about 3 weight percent.

[0214] The term "gelling agent" refers to a compound that, when homogeneously added in an amount of about 0.3 weight percent to a 50 weight percent water / 50 weight percent glycerol mixture, forms a solid medium or support matrix leading to a gel. Gelling agents include, but are not limited to, hydrogen-bond cross-linking gelling agents and ionic cross-linking gelling agents.

[0215] The term "hydrogen-bond cross-linking gelling agent" refers to a gelling agent that forms non-covalent or physical cross-links via hydrogen bonds. The hydrogen-bond cross-linking gelling agent may include one or more of galactomannan, gelatin, agarose, or konjac gum, or agar. Preferably, the hydrogen-bond cross-linking gelling agent includes agar.

[0216] The term "ionically cross-linked gelling agent" refers to a gelling agent that forms non-covalent or physical cross-links via ionic bonds. Ionically cross-linked gelling agents may include low acyl gellan, pectin, kappa carrageenan, iota carrageenan, or alginate. Preferably, the ionic cross-linked gelling agent may include low acyl gellan.

[0217] The gelling agent may comprise one or more biopolymers, which may be formed from polysaccharides.

[0218] Examples of biopolymers include gellan gum (natural gellan gum, low acyl gellan gum, high acyl gellan gum, and low acyl gellan gum are preferred), xanthan gum, alginate (alginic acid), agar, and guar gum. It may be preferable for the composition to include xanthan gum. The composition may include two biopolymers. The composition may include three biopolymers. The composition may include two biopolymers in substantially equal amounts by weight. The composition may include three biopolymers in substantially equal amounts by weight.

[0219] The gel composition may further comprise a thickening agent. The thickening agent in combination with the hydrogen-bond cross-linking gelling agent and the ionic cross-linking gelling agent surprisingly appears to support a solid medium and maintain the gel composition even when the gel composition contains high levels of glycerol.

[0220] The term "thickener" refers to a compound that, when uniformly added in an amount of 0.3 percent by weight to a 50 percent by weight water / 50 percent by weight glycerol mixture at 25°C, increases the viscosity without resulting in the formation of a gel, and causes the mixture to remain in a fluid state or to remain fluid.

[0221] The gel composition preferably comprises a thickener in the range of about 0.2 weight percent to about 5 weight percent, or about 0.5 weight percent to about 3 weight percent, or about 0.5 weight percent to about 2 weight percent, or about 1 weight percent to about 2 weight percent.

[0222] The thickening agent may comprise one or more of xanthan gum, carboxymethylcellulose, microcrystalline cellulose, methylcellulose, gum arabic, guar gum, lambda carrageenan, or starch. Preferably, the thickening agent may comprise xanthan gum.

[0223] The gel composition may further comprise a divalent cation. Preferably, the divalent cation comprises calcium ions, such as calcium lactate in solution. The divalent cation (e.g., calcium ions) may aid in gel formation in compositions that include a gelling agent, such as an ionically crosslinking gelling agent. Ionic effects may aid gel formation. The divalent cation may be present in the gel composition in a range of about 0.1 to about 1 weight percent, or about 0.5 weight percent.

[0224] The gel composition may further comprise an acid. The acid may comprise a carboxylic acid, such as levulinic acid or lactic acid.

[0225] The gel composition preferably contains some water. When the composition contains some water, the gel composition is more stable. Preferably, the gel composition contains about 8 weight percent to about 32 weight percent water, or about 15 weight percent to about 25 weight percent water, or about 18 weight percent to about 22 weight percent water, or about 20 weight percent water.

[0226] Preferably, when a gel composition is used, the aerosol-generating substrate comprises a porous medium filled with the gel composition. The term "porous" is used herein to refer to a material that provides a plurality of pores or openings that allow the passage of air through the material.

[0227] The aerosol-generating substrate may contain hydroxypropyl methylcellulose and one or more cellulose-based reinforcing agents. Aerosol-forming substrates containing a combination of hydroxypropyl methylcellulose and cellulose-based reinforcing agents may have many advantages. Incorporating hydroxypropyl methylcellulose into the aerosol-forming substrate may help improve the manufacturing process of the aerosol-forming substrate. For example, hydroxypropyl methylcellulose may reduce the overall viscosity of the slurry mixed to produce the aerosol-forming substrate. A low-viscosity slurry may flow more easily than conventional slurries, making it easier to mix, transfer, and handle during the manufacturing process. Incorporating a cellulose-based reinforcing agent into the aerosol-forming substrate may increase the tensile strength of the aerosol-forming substrate. Aerosol-forming substrates with higher tensile strength may be less likely to deteriorate or break, for example, during transportation or the manufacturing process.

[0228] Furthermore, it has been found that increasing the tensile strength of an aerosol-forming substrate using a cellulosic toughening agent can overcome the reduction in tensile strength that can be caused by the inclusion of hydroxypropyl methylcellulose, while providing the processing advantages mentioned above associated with hydroxypropyl methylcellulose.

[0229] In a preferred embodiment, the aerosol-generating substrate may comprise one or more aerosol formers, the aerosol-forming substrate having an aerosol former content of greater than 30 weight percent, hydroxypropyl methylcellulose, and one or more cellulosic strengthening agents, the one or more cellulosic strengthening agents comprising cellulose powder, and the aerosol-forming substrate having a cellulose powder content of from about 0.5 weight percent to about 50 weight percent.

[0230] The inclusion of one or more aerosol formers in the aerosol-forming substrate improves aerosol formation. The one or more aerosol formers may include glycerin. The one or more aerosol formers may include propylene glycol. The one or more aerosol formers may include a combination of glycerin and propylene glycol.

[0231] The hydroxypropyl methylcellulose is preferably a low-viscosity hydroxypropyl methylcellulose. For example, the hydroxypropyl methylcellulose may have a viscosity of 0.05 Pa / s. In some examples, the hydroxypropyl methylcellulose may have a viscosity of 0.015 Pa / s. In some examples, the hydroxypropyl methylcellulose may have a viscosity of 0.015 Pa / s to 0.05 Pa / s. Advantageously, the use of low-viscosity hydroxypropyl methylcellulose can provide benefits during the manufacturing process. The use of low-viscosity hydroxypropyl methylcellulose can form a low-viscosity slurry, which is easy to mix and move during manufacturing and processing.

[0232] The one or more cellulosic reinforcing agents may comprise cellulose fibers. Advantageously, cellulose fibers may be a cellulosic reinforcing agent that is particularly effective in increasing the tensile strength of the aerosol-forming substrate.

[0233] The aerosol-forming substrate comprising hydroxypropyl methylcellulose and one or more cellulose-based enhancers may further comprise nicotine. The nicotine may comprise one or more nicotine salts. The one or more nicotine salts may be selected from the list consisting of nicotine lactate, nicotine citrate, nicotine pyruvate, nicotine bitartrate, nicotine benzoate, nicotine pectinate, nicotine alginate, and nicotine salicylate. The nicotine may comprise a tobacco extract.

[0234] In certain embodiments, the aerosol-forming substrate comprising hydroxypropyl methylcellulose and one or more cellulosic strengthening agents may further comprise one or more carboxylic acids, including one or more of fumaric acid, lactic acid, and levulinic acid.

[0235] In certain embodiments, the aerosol-forming substrate comprising hydroxypropyl methylcellulose and one or more cellulose-based strengthening agents may further comprise tobacco particles. For example, the aerosol-forming substrate may comprise 0.01 weight percent tobacco particles, preferably at least 1 weight percent tobacco particles, even more preferably at least 2 weight percent tobacco particles, and especially preferably at least 5 weight percent tobacco particles.

[0236] In certain embodiments, the aerosol-forming substrate comprising hydroxypropyl methylcellulose and one or more cellulosic strengthening agents may further comprise carboxymethylcellulose (CMC). For example, the aerosol-forming substrate may comprise 0.5 weight percent CMC, preferably at least 1 weight percent CMC, more preferably at least 2 weight percent CMC, and even more preferably at least 4 weight percent CMC.

[0237] As mentioned above, the aerosol-generating element comprises a rod plug wrap surrounding the rod of the aerosol-generating substrate.

[0238] The rod plug wrap may comprise a paper wrapping material or a non-paper wrapping material. In a preferred embodiment, the rod plug wrap wrapping material comprises paper. Suitable paper wrapping materials for use in embodiments of the present invention are known in the art and include, but are not limited to, cigarette paper and filter plug wrap. Suitable non-paper wrapping materials for use in embodiments of the present invention are known in the art and include, but are not limited to, sheets of homogenized tobacco material and sheets of certain polymeric materials. In certain embodiments, the rod plug wrap wrapping material may be formed from a laminate material comprising multiple layers. Preferably, the rod plug wrap does not contain flame retardant compounds.

[0239] The aerosol-generating article may include a susceptor disposed within the aerosol-generating substrate. As used herein with respect to this specification, the term "susceptor" refers to a material capable of converting electromagnetic energy into heat. When located within a varying electromagnetic field, induced eddy currents in the susceptor cause heating of the susceptor.

[0240] The susceptor is preferably disposed in thermal contact with the aerosol-generating substrate, such that when the susceptor is heated, the aerosol-generating substrate is heated by the susceptor and an aerosol is generated. The susceptor may be disposed in direct physical contact with the aerosol-generating substrate.

[0241] The upstream element may advantageously prevent or limit upstream movement of the susceptor during storage, transport, and use of the aerosol-generating article.

[0242] The susceptor may be an elongated susceptor.

[0243] As used herein with respect to the present invention, the term "elongated" is used to describe a component of an aerosol-generating article that has a length that is greater than its width and thickness.

[0244] The elongated susceptor may be disposed substantially longitudinally within the aerosol-generating substrate. That is, the longitudinal axis of the elongated susceptor may be approximately parallel to the longitudinal axis of the aerosol-generating element. For example, the longitudinal axis of the elongated susceptor may be parallel to the longitudinal axis of the aerosol-generating element within ±10 degrees. The elongated susceptor is located at a radially central position within the rod of the aerosol-generating substrate and extends along the longitudinal axis of the aerosol-generating element.

[0245] The susceptor may extend from the downstream end of the aerosol-generating element towards the upstream end of the aerosol-generating element.

[0246] The susceptor may extend from the upstream end of the aerosol-generating element towards the downstream end of the aerosol-generating element.

[0247] The susceptor may extend from the upstream end of the aerosol-generating substrate to the downstream end of the aerosol-generating element, i.e., the susceptor may extend along the entire length of the aerosol-generating element.

[0248] The length of the susceptor may be substantially the same as the length of the aerosol-generating element.

[0249] The susceptor may extend partway along the length of the aerosol-generating element.

[0250] The susceptor may be spaced from the downstream end of the aerosol-generating substrate.

[0251] The susceptor may be spaced from the upstream end of the aerosol-generating element.

[0252] The susceptor may be spaced from both the downstream end and the upstream end of the aerosol-generating element.

[0253] The length of the susceptor may be less than the length of the aerosol-generating element.

[0254] The susceptor may be completely enclosed within the aerosol-generating substrate, i.e., the aerosol-generating substrate may completely surround the susceptor.

[0255] The susceptor may be in the form of a pin, rod, strip, or blade.

[0256] The susceptor may have a length of at least about 5 millimeters, at least about 6 millimeters, or at least about 8 millimeters.

[0257] The susceptor may have a length of about 15 millimeters or less, about 12 millimeters or less, or about 10 millimeters or less.

[0258] The susceptor may have a length of about 5 millimeters to about 15 millimeters, about 5 millimeters to about 12 millimeters, or about 5 millimeters to about 10 millimeters.

[0259] The susceptor may have a length of about 6 millimeters to about 15 millimeters, about 6 millimeters to about 12 millimeters, or about 6 millimeters to about 10 millimeters.

[0260] The susceptor may have a length of about 8 millimeters to about 15 millimeters, about 8 millimeters to about 12 millimeters, or about 8 millimeters to about 10 millimeters.

[0261] The susceptor may have a width of at least about 1 millimeter.

[0262] The susceptor may have a width of about 5 millimeters or less.

[0263] The susceptor may have a width of about 1 millimeter to about 5 millimeters.

[0264] The susceptor may have a thickness of at least about 0.01 millimeters to at least about 0.5 millimeters.

[0265] The susceptor may have a thickness of about 2 millimeters or less, about 500 micrometers or less, or about 100 micrometers or less.

[0266] The susceptor may have a thickness of about 10 micrometers to about 2 millimeters, about 10 micrometers to about 500 micrometers, or about 10 micrometers to about 100 micrometers.

[0267] The susceptor may have a thickness of about 0.5 millimeters to about 2 millimeters.

[0268] The susceptor may have a substantially circular cross section.

[0269] The susceptor may have a substantially constant cross section along the length of the susceptor.

[0270] When the susceptor has the shape of a strip or blade, the strip or blade may have a rectangular shape with a width of about 2 millimeters to about 8 millimeters, or about 3 millimeters to about 5 millimeters. As an example, a susceptor in the form of a strip of blade may have a width of about 4 millimeters.

[0271] When the susceptor is in the form of a strip or blade, the strip or blade may have a rectangular shape and a thickness of about 0.03 millimeters to about 0.15 millimeters, or about 0.05 millimeters to about 0.09 millimeters. As an example, a susceptor in the form of a strip of blade may have a thickness of about 0.07 millimeters or 0.06 millimeters.

[0272] The susceptor may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-generating substrate. For example, the susceptor may comprise metal or carbon.

[0273] The susceptor may include or consist of a ferromagnetic material (e.g., ferromagnetic alloy, ferritic iron, or ferromagnetic steel or stainless steel). A suitable susceptor may be or include aluminum. The susceptor may be formed from 400 series stainless steel, such as grade 410, or grade 420, or grade 430 stainless steel. Different materials dissipate different amounts of energy when placed in electromagnetic fields having similar values ​​of frequency and field strength.

[0274] Thus, the parameters of the susceptor, such as material type, length, width, and thickness, may all be modified to provide the desired power dissipation within a known electromagnetic field. The susceptor may be heated to temperatures in excess of 250°C.

[0275] A suitable susceptor may include a non-metallic core having a metal layer disposed thereon (e.g., a metal track formed on the surface of a ceramic core). The susceptor may have a protective outer layer, such as a protective ceramic or glass layer, encapsulating the susceptor. The susceptor may also include a protective coating formed of glass, ceramic, or an inert metal formed over a core of susceptor material.

[0276] The susceptor may be a multi-material susceptor and may include a first susceptor material and a second susceptor material.

[0277] The aerosol-generating article according to the present invention may additionally comprise a downstream section downstream of the aerosol-generating element. If present, the downstream section is provided immediately downstream of the aerosol-generating element and extends from the downstream end of the aerosol-generating article to the downstream end of the aerosol-generating article.

[0278] The downstream section may include one or more components.

[0279] For example, the downstream section may comprise one or more of a support element, an aerosol cooling element, and a mouthpiece element.

[0280] At least one of the support element and the aerosol cooling element may be in the form of a hollow tubular element, hi some embodiments, both the support element and the aerosol cooling element are in the form of hollow tubular elements, which may differ in length, inner diameter, or both.

[0281] In the aerosol-generating article according to the present invention, such hollow tubular elements provide unrestricted flow channels. This means that the hollow tubular elements provide negligible levels of RTD. As used herein with respect to the present invention, the term "negligible levels of RTD" is used to describe an RTD of less than 1 mmH2O per 10 millimeters of length of the hollow tubular substrate element, less than 0.4 mmH2O per 10 millimeters of length of the hollow tubular substrate element, or less than 0.1 mmH2O per 10 millimeters of length of the hollow tubular substrate element. Thus, the flow channels should be free of any components that would impede longitudinal air flow. Preferably, the flow channels are substantially empty.

[0282] The hollow tubular element may have an overall length of at least about 6 millimeters, preferably at least about 8 millimeters, at least about 10 millimeters, at least about 12 millimeters, or at least about 15 millimeters.

[0283] The hollow tubular element may have an overall length of about 30 millimeters or less, 25 millimeters or less, or about 23 millimeters or less.

[0284] The hollow tubular element may have an overall length of about 10 millimeters to about 30 millimeters, about 10 millimeters to about 25 millimeters, or about 10 millimeters to about 23 millimeters.

[0285] The hollow tubular element may have an overall length of about 12 millimeters to about 30 millimeters, about 12 millimeters to about 25 millimeters, or about 12 millimeters to about 23 millimeters.

[0286] The hollow tubular element may have an overall length of about 12 millimeters to about 30 millimeters, about 12 millimeters to about 25 millimeters, or about 12 millimeters to about 23 millimeters.

[0287] The overall length of the hollow tubular element may be selected based on the desired overall length of the aerosol-generating article.

[0288] The hollow tubular element may be formed from any suitable material or combination of materials. For example, the hollow tubular element may be formed from one or more materials selected from the group consisting of cellulose acetate, paper-based materials such as paper or cardboard, crimped paper, and polymeric materials such as low-density polyethylene (LDPE). Other suitable materials include polyhydroxyalkanoate (PHA) fibers.

[0289] In some embodiments, a ventilation zone may be provided downstream of the aerosol-generating element. Satisfactory cooling of the aerosol stream generated upon heating of the aerosol-generating substrate and drawn through the hollow tubular element may be achieved by providing a ventilation zone along the hollow tubular element itself or along an intermediate element provided between the hollow tubular element and the downstream end of the aerosol-generating article. Without wishing to be bound by theory, the temperature reduction caused by admitting cooler ambient air through the ventilation zone into the aerosol-generating article downstream of the aerosol-generating element may have a beneficial effect on aerosol particle nucleation and growth.

[0290] The ventilation zone may include a plurality of perforations through the tubular wall of the hollow tubular element. The ventilation zone may comprise at least one circumferential row of perforations. The ventilation zone may include two circumferential rows of perforations. For example, the perforations may be formed online during manufacture of the aerosol-generating article. Each circumferential row of perforations may include 8 to 30 perforations.

[0291] As mentioned above, the downstream section of the aerosol-generating article is located downstream of the aerosol-generating substrate and may comprise a mouthpiece element located at the downstream or mouth or proximal end of the aerosol-generating article.

[0292] The mouthpiece element may be a mouthpiece filter element. The mouthpiece element may comprise at least one filter segment. For example, the mouthpiece element may comprise one or more segments of fibrous filtration material. Suitable fibrous filtration materials are known in the art. For example, the at least one mouthpiece filter segment may comprise a cellulose acetate filter segment formed from cellulose acetate tow.

[0293] The mouthpiece element may consist of a single filter segment. The mouthpiece element may include two or more filter segments abutting and axially aligned in end-to-end relationship with one another.

[0294] Parameters or characteristics described herein with respect to the mouthpiece element as a whole may be equally applied to the filter segment of the mouthpiece element.

[0295] The mouthpiece element may have a low particulate filtration efficiency.

[0296] The mouthpiece element may have an RTD of about 25 millimeters H2O or less, about 20 millimeters H2O or less, or about 15 millimeters H2O or less.

[0297] The mouthpiece element may have an RTD of at least about 10 millimeters H2O.

[0298] The mouthpiece element may have an RTD of about 10 millimeters HO to about 25 millimeters HO, about 10 millimeters HO to about 20 millimeters HO, or about 10 millimeters HO to about 15 millimeters HO.

[0299] The mouthpiece element preferably has a substantially circular cross section.

[0300] Preferably, the mouthpiece element has an outer diameter that is substantially the same as the outer diameter of the aerosol-generating article.

[0301] The mouthpiece element may have a length of at least about 3 millimeters, or at least about 5 millimeters.

[0302] The length of the mouthpiece element may be about 14 millimeters or less, preferably 12 millimeters or less, 10 millimeters or less, or about 9 millimeters or less.

[0303] The length of the mouthpiece element may be from about 3 millimeters to about 11 millimeters, or from about 3 millimeters to about 9 millimeters.

[0304] The length of the mouthpiece element may be from about 5 millimeters to about 11 millimeters, or from about 5 millimeters to about 9 millimeters.

[0305] For example, the mouthpiece element may have a length of about 7 millimeters.

[0306] The length of the mouthpiece element may be selected based on the desired overall length of the aerosol-generating article.

[0307] The mouthpiece element may be surrounded by a plug wrap.

[0308] The mouthpiece element may be non-vented so that air does not enter the aerosol-generating article along the mouthpiece element.

[0309] The mouthpiece element may be connected to one or more of the adjacent components of the aerosol-generating article by a tipping wrapper.

[0310] The aerosol-generating article may define a mouth-end cavity at the downstream end of the aerosol-generating article. For example, the mouthpiece element may itself be in the form of a hollow tubular element. Alternatively, the mouthpiece element may include a solid segment immediately upstream of the hollow tubular segment provided at the downstream end of the mouthpiece element. As a further alternative, the mouth-end cavity may be defined by an outer wrapper of the mouthpiece element that extends beyond the downstream end of the segment of filtration material of the mouthpiece element.

[0311] The aerosol-generating article may have a total length of at least about 35 millimeters, at least about 38 millimeters, at least about 40 millimeters, or at least about 42 millimeters.

[0312] The aerosol-generating article may have a total length of about 100 millimeters or less, about 70 millimeters or less, about 60 millimeters or less, or 50 millimeters or less.

[0313] The aerosol-generating article may have a total length of about 35 millimeters to about 100 millimeters, about 35 millimeters to about 70 millimeters, about 35 millimeters to about 60 millimeters, or about 35 millimeters to about 50 millimeters.

[0314] The aerosol-generating article may have a total length of about 38 millimeters to about 100 millimeters, about 38 millimeters to about 70 millimeters, about 38 millimeters to about 60 millimeters, or about 38 millimeters to about 50 millimeters.

[0315] The aerosol-generating article may have a total length of about 40 millimeters to about 100 millimeters, about 40 millimeters to about 70 millimeters, about 40 millimeters to about 60 millimeters, or about 40 millimeters to about 50 millimeters.

[0316] The aerosol-generating article may have a total length of about 42 millimeters to about 100 millimeters, about 42 millimeters to about 70 millimeters, about 42 millimeters to about 60 millimeters, or about 42 millimeters to about 50 millimeters.

[0317] For example, the aerosol-generating article may have a total length of about 45 millimeters.

[0318] Preferably, the aerosol-generating article has a substantially circular cross-section.

[0319] The aerosol-generating article may have an outer diameter of at least about 5 millimeters, at least about 6 millimeters, or at least about 7 millimeters.

[0320] The aerosol-generating article may have an outer diameter of about 12 millimeters or less, about 10 millimeters or less, or about 8 millimeters or less.

[0321] The aerosol-generating article may have an outer diameter of from about 5 millimeters to about 12 millimeters, or from about 5 millimeters to about 10 millimeters, or from about 5 millimeters to about 8 millimeters.

[0322] The aerosol-generating article may have an outer diameter of from about 6 millimeters to about 12 millimeters, or from about 6 millimeters to about 10 millimeters, or from about 6 millimeters to about 8 millimeters.

[0323] The aerosol-generating article may have an outer diameter of from about 7 millimeters to about 12 millimeters, or from about 7 millimeters to about 10 millimeters, or from about 7 millimeters to about 8 millimeters.

[0324] For example, the aerosol-generating article may have an outer diameter of about 7.1 millimeters.

[0325] According to a second aspect of the present invention, there is provided an aerosol generating system comprising an aerosol-generating article according to the first aspect of the present invention and an aerosol generating apparatus configured to heat the aerosol-generating substrate of the aerosol-generating article.

[0326] The aerosol-generating device includes means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate. Preferably, the aerosol-generating device comprises a housing defining a cavity configured to receive an aerosol-generating article, and means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate when the aerosol-generating article is received in the cavity.

[0327] The aerosol generating device may be a handheld aerosol generating device.

[0328] The aerosol generating device may be an electrically operated aerosol generating device.

[0329] The aerosol generating device may include a power source and control electronics.

[0330] The aerosol generating device may include a battery and control electronics.

[0331] The aerosol-generating device may be configured to heat the aerosol-generating substrate internally, i.e. the aerosol-generating device may be configured to supply heat to the aerosol-generating substrate from a location internal to the aerosol-generating article.

[0332] For example, in some embodiments, the aerosol generating device comprises a heater element configured to be inserted into the aerosol generating element when the aerosol-generating article is received within the cavity of the aerosol generating device.

[0333] In another embodiment, the aerosol-generating article includes a susceptor element provided in a position within the aerosol-generating element, and the aerosol-generating device includes an inductor coil positioned on or within the housing. The aerosol-generating device's power supply is connected to the inductor coil and configured to provide a high-frequency oscillating current to the inductor coil. This generates an alternating magnetic field that induces a voltage in the susceptor element. The induced voltage causes a current to flow in the susceptor element, which causes Joule heating of the susceptor element, which in turn heats the aerosol-generating substrate. The aerosol-generating device may be capable of generating a fluctuating electromagnetic field having a magnetic field strength (H-field strength) of 1 to 5 kiloamperes per meter (kA / m), preferably 2 to 3 kA / m, e.g., about 2.5 kA / m.

[0334] The aerosol-generating device may be configured to heat the aerosol-generating substrate externally, i.e., the aerosol-generating device may be configured to supply heat to the aerosol-generating substrate from a location external to the aerosol-generating article. For example, in some embodiments, the aerosol-generating device comprises heater elements located around the periphery of the cavity and configured to heat the aerosol-generating substrate of the aerosol-generating article from external to the aerosol-generating element of the aerosol-generating article. [Brief explanation of the drawings]

[0335] [Figure 1] FIG. 1 shows a schematic cross-sectional side view of an aerosol-generating article according to an embodiment of the present invention. [Figure 2] FIG. 2 shows a schematic cross-sectional side view of another aerosol-generating article according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0336] The present invention is defined in the claims. However, below 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 any other example, embodiment, or aspect described herein.

[0337] Example 1: 1. An aerosol-generating article for generating an aerosol upon heating, the aerosol-generating article comprising: an aerosol-generating element comprising a rod of aerosol-generating substrate surrounded by a rod plug wrap; an upstream element located upstream of the aerosol-generating element, the upstream element comprising a segment of material surrounded by a first wrapper; and a second wrapper surrounding both the upstream element and the aerosol-generating element, wherein the first wrapper, the second wrapper, or both, comprise a flame-retardant coating composition comprising one or more flame-retardant compounds at a location along the segment of material of the upstream element.

[0338] Example 2: 10. The aerosol-generating article of claim 1, wherein the first wrapper comprises a wrapping substrate, and the flame retardant composition is provided on a surface of the wrapping substrate facing the segment of material of the upstream element, a surface of the wrapping substrate facing away from the segment of material of the upstream element, or both.

[0339] Example 3: 10. The aerosol-generating article of example 1, wherein the first wrapper comprises a wrapping substrate impregnated with the flame retardant composition.

[0340] Example 4: 10. The aerosol-generating article of claim 1, wherein the second wrapper comprises a wrapping substrate impregnated with the flame retardant composition.

[0341] Example 5: 10. The aerosol-generating article of claim 1, wherein the first wrapper comprises a wrapping substrate comprising the flame retardant composition.

[0342] Example 6: 10. The aerosol-generating article of claim 1, wherein the second wrapper comprises a wrapping substrate comprising the flame retardant composition.

[0343] Example 7: 7. An aerosol-generating article according to any one of Examples 1 to 6, wherein the flame-retardant composition comprises a polymer and at least one mono-, di-, and / or tricarboxylic acid, at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid, and a hydroxide or a mixed salt based on a salt of an alkali or alkaline earth metal, wherein the at least one mono-, di-, and / or tricarboxylic acid and the hydroxide or salt forms a carboxylate salt, and the at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid and the hydroxide or salt forms a phosphate salt.

[0344] Example 8: The aerosol-generating article of example 7, wherein the flame retardant composition comprises a carbonate of an alkali or alkaline earth metal.

[0345] Example 9: The flame retardant composition comprises at least one C 10 An aerosol-generating article according to any one of Examples 1 to 6, comprising cellulose modified with the above fatty acids, tall oil fatty acid (TOFA), phosphorylated linseed oil, or phosphorylated lower corn oil.

[0346] Example 10: An aerosol-generating article according to any one of Examples 1 to 9, wherein neither the first wrapper nor the second wrapper contains metal.

[0347] Example 11: 11. An aerosol-generating article according to any one of Examples 2 to 10, wherein the flame retardant composition is applied as a coating to at least one side of the wrapping substrate of the wrapper by a size press, spraying, printing or coating-based application process.

[0348] Example 12: 12. An aerosol-generating article according to any one of Examples 2 to 11, wherein the wrapping substrate of the first wrapper or the second wrapper, or both, is a paper material having a weight of from 20 gsm to 110 gsm, preferably from 20 gsm to 40 gsm.

[0349] Example 13: An aerosol-generating article according to any one of Examples 1 to 12, wherein the segment of material comprises a plug of cellulose acetate.

[0350] Example 14: An aerosol-generating article according to any one of Examples 1 to 13, wherein the segment of material comprises a hollow tubular body.

[0351] Example 15: An aerosol-generating article according to any one of Examples 1 to 14, wherein the segment of material comprises a spirally wound sheet defining a plurality of longitudinally extending channels.

[0352] Example 16: An aerosol-generating article as described in Example 15, wherein the segment of material comprises a tubular portion defining an inner region of the upstream element, and the spiral-wound sheet is disposed within the tubular portion such that a plurality of longitudinally extending channels are defined within the inner region.

[0353] Example 17: 17. The aerosol-generating article of example 15 or 16, wherein the spirally wound sheet has a basis weight of about 100 grams per square meter or less.

[0354] Example 18: An aerosol-generating article according to any one of Examples 1 to 17, wherein the aerosol-generating substrate comprises at least 10 weight percent aerosol formers.

[0355] Example 19: An aerosol-generating article according to any one of Examples 1 to 18, wherein the aerosol-generating substrate comprises a plurality of strips of tobacco material.

[0356] Example 20: 19. An aerosol-generating article according to any one of Examples 1 to 18, wherein the aerosol-generating substrate comprises a plurality of pellets or granules of tobacco material.

[0357] Example 21: An aerosol-generating article according to any one of Examples 1 to 18, wherein the aerosol-generating substrate comprises one or more sheets of homogenized tobacco material.

[0358] Example 22: An aerosol-generating article according to any one of Examples 1 to 18, wherein the aerosol-generating substrate comprises a gel composition comprising nicotine, at least one gelling agent and an aerosol former.

[0359] Example 23: 19. An aerosol-generating article according to any one of Examples 1 to 18, wherein the aerosol-generating substrate comprises hydroxypropyl methylcellulose and one or more cellulosic reinforcing agents.

[0360] Example 24: An aerosol-generating article as described in any one of Examples 1 to 23, wherein the rod plug wrap does not contain a flame retardant compound.

[0361] Example 25: An aerosol-generating article according to any one of Examples 2 to 24, wherein the wrapping substrate of the first wrapper has a basis weight of from 20 grams per square meter to 120 grams per square meter.

[0362] Example 26: An aerosol-generating article according to any one of Examples 2 to 24, wherein the wrapping substrate of the first wrapper has a thickness of from 20 micrometers to 110 micrometers.

[0363] Example 27: An aerosol-generating article according to any one of Examples 2 to 24, wherein the wrapping substrate of the second wrapper has a basis weight of from 20 grams per square meter to 60 grams per square meter.

[0364] Example 28: An aerosol-generating article according to any one of Examples 2 to 24, wherein the wrapping substrate of the second wrapper has a thickness of 40 micrometers to 70 micrometers.

[0365] Example 29: An aerosol-generating article according to any one of Examples 1 to 28, wherein the ratio of the total weight of the flame retardant compounds to the total dry weight of the wrapper can be at least about 0.02.

[0366] Example 30: 30. The aerosol-generating article of any one of Examples 1-29, wherein the ratio of the total weight of the flame retardant compounds to the total dry weight of the wrapper is about 0.20 or less.

[0367] Example 31: An aerosol-generating article described in any one of Examples 1 to 30, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the treated portion of the wrapper extends over at least 10 percent of the outer surface of the segment of material of the upstream element.

[0368] Example 31: An aerosol-generating article described in any one of Examples 1 to 31, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the treated portion of the wrapper extends over at least 40 percent of the outer surface of the segment of material of the upstream element.

[0369] Example 32: An aerosol-generating article described in any one of Examples 1 to 31, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the treated portion of the wrapper extends over at least 80 percent of the outer surface of the segment of material of the upstream element.

[0370] Example 34: An aerosol-generating article described in any one of Examples 1 to 33, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the treated portion of the wrapper extends over at least 90 percent of the outer surface of the segment of material of the upstream element.

[0371] Example 35: An aerosol-generating article described in any one of Examples 1 to 34, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the treated portion of the wrapper extends over at least 95 percent of the outer surface of the segment of material of the upstream element.

[0372] Example 36: An aerosol-generating article described in any one of Examples 1 to 35, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the length of the treated portion of the wrapper is at least 10 percent of the length of the segment of material of the upstream element.

[0373] Example 37: An aerosol-generating article described in any one of Examples 1 to 36, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the length of the treated portion of the wrapper is at least 40 percent of the length of the segment of material of the upstream element.

[0374] Example 38: An aerosol-generating article described in any one of Examples 1 to 37, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the length of the treated portion of the wrapper is at least 80 percent of the length of the segment of material of the upstream element.

[0375] Example 39: An aerosol-generating article described in any one of Examples 1 to 38, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the length of the treated portion of the wrapper is at least 90 percent of the length of the segment of material of the upstream element.

[0376] Example 40: An aerosol-generating article described in any one of Examples 1 to 39, wherein the flame retardant composition is provided in a treated portion of the wrapper, and the length of the treated portion of the wrapper is at least 95 percent of the length of the segment of material of the upstream element.

[0377] Example 41: An aerosol-generating article described in any one of Examples 1 to 40, wherein the flame retardant composition is provided in the treated portion of the wrapper, and at least about 10 grams of the flame retardant composition is provided in the treated portion per square meter of surface area of ​​the treated portion.

[0378] Example 42: 42. An aerosol-generating article according to any one of Examples 1 to 41, wherein a flame retardant composition is provided in the treated portion of the wrapper, and wherein no more than 100 grams of the flame retardant composition is provided in the treated portion per square meter of surface area of ​​the treated portion.

[0379] Example 43: An aerosol-generating article described in any one of Examples 1 to 42, wherein a flame retardant composition is provided in the treated portion of the wrapper, and the content of the flame retardant compound in the treated portion is such that the aerosol-generating article does not ignite when heated to 500 degrees Celsius for at least 5 seconds using a resistive heating coil.

[0380] Example 44: An aerosol-generating article described in any one of Examples 1 to 43, wherein a flame retardant composition is provided in the treated portion of the wrapper, and the content of the flame retardant compound in the treated portion is such that the aerosol-generating article does not ignite when heated to 500 degrees Celsius for at least 30 seconds using a resistive heating coil.

[0381] Example 45: An aerosol-generating article according to any one of Examples 1 to 44, wherein the upstream element has an outer diameter of at least 5 millimeters.

[0382] Example 46: 46. ​​An aerosol-generating article according to any one of Examples 1 to 45, wherein the upstream element has an outer diameter of 12 millimeters or less.

[0383] Example 47: An aerosol-generating article according to any one of Examples 1 to 46, wherein the upstream element has a length of at least 1 millimeter.

[0384] Example 48: An aerosol-generating article according to any one of Examples 1 to 47, wherein the upstream element has a length of 25 millimeters or less.

[0385] Example 49: The aerosol-generating article of any one of Examples 1 to 48, wherein the upstream element has a mass of at least 10 milligrams.

[0386] Example 50: 50. The aerosol-generating article of any one of Examples 1 to 49, wherein the upstream element has a weight of 100 milligrams or less.

[0387] Example 51: An aerosol-generating article according to any one of Examples 1 to 50, wherein the segment of material of the upstream element has an RTD of at least 1 millimeter HO.

[0388] Example 52: 52. An aerosol-generating article according to any one of Examples 1 to 51, wherein the segment of material of the upstream element has an RTD of 10 millimeters H2O or less.

[0389] Example 53: An aerosol-generating system comprising an electrically operated aerosol-generating device and the aerosol-generating article of any one of Examples 1 to 52, wherein the aerosol-generating device comprises means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate.

[0390] The embodiments will now be further described with reference to the accompanying drawing figures.

[0391] 1 comprises a rod 12 of aerosol-generating substrate 12 and a downstream section 14 located downstream of the rod 12 of aerosol-generating substrate. Additionally, the aerosol-generating article 10 comprises an upstream section 16 located upstream of the rod 12 of aerosol-generating substrate. Thus, the aerosol-generating article 10 may extend from an upstream or distal end 18 to a downstream or oral end 20.

[0392] The aerosol-generating article has a total length of about 45 millimeters.

[0393] The downstream section 14 comprises a support element 22 located immediately downstream from the rod 12 of the aerosol-generating substrate, the support element 22 being longitudinally aligned with the rod 12. In the embodiment of Figure 1, the upstream end of the support element 18 abuts the downstream end of the rod 12 of the aerosol-generating substrate. The downstream section 14 further comprises an aerosol cooling element 24 located immediately downstream from the support element 22, the aerosol cooling element 24 being longitudinally aligned with the rod 12 and the support element 22. In the embodiment of Figure 1, the upstream end of the aerosol cooling element 24 abuts the downstream end of the support element 22. In the embodiment of Figure 1, the support element 22 and the aerosol cooling element 24 together define an intermediate hollow section 80 of the aerosol-generating article 10.

[0394] The support element 22 includes a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 that extends entirely from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 26. The interior cavity 28 is substantially empty, thereby permitting substantially unrestricted airflow therealong.

[0395] The first hollow tubular segment 26 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter of about 1.9 millimeters. Accordingly, the peripheral wall thickness of the first hollow tubular segment 26 is about 2.67 millimeters.

[0396] The aerosol cooling element 24 includes a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 that extends from an upstream end 38 of the second hollow tubular segment all the way to a downstream end 40 of the second hollow tubular segment 34. The interior cavity 36 is substantially empty, thus permitting substantially unrestricted airflow along the interior cavity 36.

[0397] The second hollow tubular segment 34 has a length of approximately 8 millimeters, an outer diameter of approximately 7.25 millimeters, and an inner diameter of approximately 3.25 millimeters. Thus, the peripheral wall thickness of the second hollow tubular segment 34 is approximately 2 millimeters. Thus, the ratio between the inner diameter of the first hollow tubular segment 26 and the inner diameter of the second hollow tubular segment 34 is approximately 0.75.

[0398] The aerosol-generating article 10 includes a ventilation zone 60 provided along the second hollow tubular segment 34. More specifically, the ventilation zone is provided approximately 2 millimeters from the upstream end of the second hollow tubular segment 34. The ventilation level of the aerosol-generating article 10 is approximately 25 percent.

[0399] 1, downstream section 14 further comprises mouthpiece element 42 located downstream of intermediate hollow section 80. More particularly, mouthpiece element 42 is positioned immediately downstream of aerosol cooling element 24. As shown in the drawing of FIG. 1, the upstream end of mouthpiece element 42 abuts downstream end 40 of aerosol cooling element 24.

[0400] Mouthpiece element 42 is provided in the form of a cylindrical plug of low density cellulose acetate 44. Mouthpiece element 42 has a length of about 12 millimeters and an outer diameter of about 7.25 millimeters.

[0401] The rod 12 includes an aerosol-generating substrate of one of the types described above.

[0402] The aerosol-generating substrate rod 12 has an outer diameter of about 7.25 millimeters and a length of about 12 millimeters.

[0403] The aerosol-generating article 10 further includes an elongated susceptor 46 within the rod 12 of the aerosol-generating substrate. More specifically, the susceptor 46 is disposed substantially longitudinally within the aerosol-generating substrate, approximately parallel to the longitudinal direction of the rod 12. As shown in the drawing in FIG. 1 , the susceptor 46 is positioned at a radially central location within the rod and effectively extends along the longitudinal axis of the rod 12. More specifically, the susceptor 46 is in thermal contact with the aerosol-generating substrate. The susceptor 46 extends completely from the upstream end to the downstream end of the rod 12. In practice, the susceptor 46 has substantially the same length as the rod 12 of the aerosol-generating substrate.

[0404] In the embodiment of FIG. 1, the susceptor 46 is provided in the form of a strip, having a length of about 12 millimeters, a thickness of about 60 micrometers, and a width of about 4 millimeters.

[0405] The upstream section 16 includes an upstream element 48 located immediately upstream of the rod 12 of the aerosol-generating substrate, and the upstream element 48 is longitudinally aligned with the rod 12. In the embodiment of Figure 1, the downstream end of the upstream element 48 abuts the upstream end of the rod 12 of the aerosol-generating substrate. This advantageously prevents the susceptor 46 from becoming dislodged. Furthermore, this ensures that a consumer cannot accidentally come into contact with the heated susceptor 46 after use.

[0406] The upstream element 48 comprises a segment of material 50 in the form of a cylindrical plug of cellulose acetate and a first wrapper 52 surrounding the segment of material 50. The segment of material 50 has a length of approximately 5 millimeters. The RTD of the segment of material 50 is approximately 30 millimeters HO.

[0407] The aerosol-generating article 10 further comprises a bonded wrapper 54 that attaches the upstream element 48 to the remaining components of the aerosol-generating article. In the embodiment of Figure 1, a single bonded wrapper 54 is shown surrounding and holding the upstream element 48, rod 12, and downstream section 14 together to form the aerosol-generating article.

[0408] However, it will be apparent that alternative configurations are possible in which two or more bonding wrappers are employed to assemble different components of the aerosol-generating article. For example, a first bonding wrapper can be used to attach the support element 22 to the aerosol cooling element 24, and the resulting assembly can then be attached to the upstream section 16 and rod 12 by a second bonding wrapper. The resulting combination of components can then be attached to the mouthpiece element 42 by a tipping wrapper.

[0409] First wrapper 52 includes a flame retardant composition at a location along segment of material 50. More particularly, first wrapper 52 is formed of a wrapping substrate having a flame retardant coating applied to a surface of the wrapping substrate facing segment of material 50.

[0410] More specifically, the flame-retardant coating is provided at least on a treated portion of the first wrapper 52 extending between the proximal and distal ends of the segment of material 50. The treated portion includes approximately 15 grams of flame-retardant compound per square meter of surface area of ​​the treated portion. Thus, the treated portion of the wrapper 52 has a total basis weight greater than the basis weight of the wrapping substrate. In the embodiment of FIG. 1, the treated portion has a length that substantially matches the length of the segment of material 50 and extends across substantially the entire outer surface area of ​​the segment of material 50.

[0411] As shown in the drawing of Figure 1, the aerosol-generating article 10 further comprises a wrapper 70 surrounding the rod of aerosol-generating substrate 12. The wrapper 70 is separate and distinct from the first wrapper 52 surrounding the segment of material 50. Neither the first wrapper 52 nor the wrapper 70 includes metal foil. The aforementioned combined wrapper 54 surrounds both the first wrapper 52 surrounding the segment of material 50 and the wrapper 70 surrounding the rod of aerosol-generating substrate 12.

[0412] The aerosol-generating article 110 shown in FIG. 2 has many features in common with the aerosol-generating article 10 of FIG. 1 and, to the extent that it differs from the aerosol-generating article 10, will be described below.

[0413] As shown in FIG. 2, the aerosol-generating article 110 comprises a rod 12 of aerosol-generating substrate 12 and a modified downstream section 114 located downstream of the rod 12 of aerosol-generating substrate.

[0414] Similar to the downstream section 14 of the aerosol-generating article 10 of Figure 1, the modified downstream section 114 of the aerosol-generating article 110 of Figure 2 comprises a support element 22 positioned immediately downstream of the rod 12 of the aerosol-generating substrate, the support element 22 being longitudinally aligned with the rod 12, and the upstream end of the support element 22 abutting the downstream end of the rod 12 of the aerosol-generating substrate.

[0415] Additionally, the modified downstream section 114 includes an aerosol cooling element 134 located immediately downstream of the support element 22, the aerosol cooling element 134 being longitudinally aligned with the rod 12 and the support element 22. More specifically, the upstream end of the aerosol cooling element 134 abuts the downstream end of the support element 22.

[0416] In contrast to the downstream section 14 of the aerosol-generating article 10, the aerosol cooling element 134 of the modified downstream section 114 comprises a plurality of longitudinally extending channels that provide low or substantially zero resistance to the passage of air through the rod. More specifically, the aerosol cooling element 134 is preferably formed from an imperforate sheet material selected from the group including metal foil, polymeric sheet, and substantially imperforate paper or cardboard. In particular, in the embodiment illustrated in FIG. 2, the aerosol cooling element 134 is provided in the form of a crimped sheet and sheet assembly of polylactic acid (PLA). The aerosol cooling element 134 has a length of approximately 8 millimeters and an outer diameter of approximately 7.25 millimeters.

[0417] Similar to the embodiment of Figure 1, the aerosol-generating article 110 of Figure 2 comprises an upstream section 16 including an upstream element 48 located immediately upstream of the rod 12 of the aerosol-generating substrate, the upstream element 48 being longitudinally aligned with the rod 12. The upstream element 48 comprises a segment of material 50 in the form of a cylindrical plug of cellulose acetate and a first wrapper 52 surrounding the segment of material 50. The segment of material 50 has a length of approximately 5 millimeters. The RTD of the segment of material 50 is approximately 30 millimeters HO.

[0418] The aerosol-generating article 10 further comprises a bonded wrapper 54 that attaches the upstream element 48 to the remaining components of the aerosol-generating article. In the embodiment of Figure 1, a single bonded wrapper 54 is shown surrounding and holding the upstream element 48, rod 12, and downstream section 14 together to form the aerosol-generating article.

[0419] First wrapper 52 includes a flame retardant composition at a location along segment of material 50. More particularly, first wrapper 52 is formed of a wrapping substrate having a flame retardant coating applied to a surface of the wrapping substrate facing away from segment of material 50.

[0420] More specifically, the flame-retardant coating is provided at least on a treated portion of the first wrapper 52 extending between the proximal and distal ends of the segment of material 50. The treated portion includes approximately 15 grams of flame-retardant compound per square meter of surface area of ​​the treated portion. Thus, the treated portion of the wrapper 52 has a total basis weight greater than the basis weight of the wrapping substrate. In the embodiment of FIG. 2, the treated portion has a length that substantially matches the length of the segment of material 50 and extends substantially across the entire outer surface area of ​​the segment of material 50.

[0421] 2, the bonded wrapper 54 that surrounds the upstream element 48 and attaches it to the remainder of the aerosol-generating article also includes a flame retardant at a location along the segment of material 50 of the upstream element 48. More particularly, the bonded wrapper 54 is formed of a wrapping substrate having a flame retardant coating applied to a surface of the wrapping substrate facing away from the segment of material 50.

[0422] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like are understood to be modified in all instances by the term "about." Also, all ranges include the maximum and minimum values ​​disclosed, as well as any intermediate ranges contained therein, whether or not specifically recited herein. Thus, in this context, a numerical value A would be understood as A ± 5%. In this context, a numerical value A can be considered to include values ​​that fall within the typical standard error of measurement for the property that A modifies. In some instances, as used in the appended claims, a numerical value A may deviate by the percentages recited above, so long as the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the maximum and minimum values ​​disclosed, as well as any intermediate ranges contained therein, whether or not specifically recited herein.

Claims

1. An aerosol-generating article comprising: an aerosol-generating element comprising a rod of aerosol-generating substrate surrounded by a rod plug wrap; an upstream element located upstream of the aerosol-generation element, the upstream element including a segment of material surrounded by a first wrapper; a second wrapper surrounding both the upstream element and the aerosol-generation element; The aerosol-generating article wherein the first wrapper or the second wrapper, or both, comprise a flame retardant composition comprising one or more flame retardant compounds at a location along the material segment of the upstream element.

2. 2. The aerosol-generating article of claim 1, wherein the first wrapper comprises a wrapping substrate, and the flame retardant composition is provided on a surface of the wrapping substrate facing the segment of material of the upstream element, a surface of the wrapping substrate facing away from the segment of material of the upstream element, or both.

3. 3. The aerosol-generating article of claim 1 or 2, wherein the second wrapper comprises a wrapping substrate, and the flame-retardant composition is provided on a surface of the wrapping substrate facing the segment of material of the upstream element, a surface of the wrapping substrate facing the opposite side of the upstream element from the segment of material, or both.

4. 4. The aerosol-generating article of claim 1, wherein the flame-retardant composition comprises a polymer and at least one mono-, di-, and / or tricarboxylic acid, at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid, and a hydroxide or a mixed salt based on a salt of an alkali or alkaline earth metal, wherein the at least one mono-, di-, and / or tricarboxylic acid and the hydroxide or salt form a carboxylate salt, and the at least one polyphosphoric acid, pyrophosphoric acid, and / or phosphoric acid and the hydroxide or salt form a phosphate salt.

5. The flame retardant composition comprises at least one C 10 4. The aerosol-generating article according to claim 1, comprising cellulose modified with any one of the above fatty acids, tall oil fatty acid (TOFA), phosphorylated linseed oil, and phosphorylated downstream corn oil.

6. 6. The aerosol-generating article of claim 2, wherein the flame retardant composition is applied as a coating to at least one side of the wrapping substrate of the wrapper by a size press, spraying, printing or coating-based application process.

7. An aerosol-generating article according to any one of claims 1 to 6, wherein the segment of material comprises a plug of cellulose acetate.

8. An aerosol-generating article according to any preceding claim, wherein the segment of material comprises a hollow tubular body.

9. 9. An aerosol-generating article according to any preceding claim, wherein the segment of material comprises a spirally wound sheet defining a plurality of longitudinally extending channels.

10. 10. The aerosol-generating article of any one of claims 1 to 9, wherein the aerosol-generating substrate comprises at least about 10 percent by weight of an aerosol former.

11. 11. An aerosol-generating article according to any preceding claim, wherein the aerosol-generating substrate comprises a plurality of strips of tobacco material.

12. An aerosol-generating article according to any one of claims 1 to 10, wherein the aerosol-generating substrate comprises one or more sheets of homogenized tobacco material.

13. 11. The aerosol-generating article of claim 1, wherein the aerosol-generating substrate comprises a gel composition comprising nicotine, at least one gelling agent, and an aerosol former.

14. 11. The aerosol-generating article of claim 1, wherein the aerosol-generating substrate comprises hydroxypropyl methylcellulose and one or more cellulosic reinforcing agents.

15. 15. An aerosol-generating system comprising an electrically operated aerosol-generating device and an aerosol-generating article according to any one of claims 1 to 14, wherein the aerosol-generating device comprises means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate.

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