Novel aerosol-generating substrate comprising plant particles

Abstract

An aerosol-generating substrate (40)(114) for use in an aerosol-generating article or system comprises: at least 50 percent by weight of plant particles, on a dry weight basis; at least 10 percent by weight of aerosol former, on a dry weight basis; and one or more hydrocolloid binders. The total amount of hydrocolloid binder is less than or equal to 5 percent by weight of the aerosol-generating substrate (40((1140), on a dry weight basis. The weight ratio of plant particles to aerosol former in the aerosol-generating substrate (40)(114) is at least 2.5. The aerosol-generating substrate (40)(114)is in the form of a plurality of beads or granules.

Description

[0001] NOVEL AEROSOL-GENERATING SUBSTRATE COMPRISING PLANT PARTICLES

[0002] The present invention relates to a novel aerosol-generating substrate comprising plant particles, to an article including the aerosol-generating substrate and to a method of producing the aerosol-generating substrate.

[0003] A number of aerosol-generating articles in which an aerosol-generating substrate, such as tobacco, is heated rather than combusted have been proposed in the art. In these aerosolgenerating articles, an aerosol is typically generated by heating the aerosol-generating substrate to a predetermined temperature. For example, smoking articles have been disclosed in which an aerosol is generated by electrical heating or by the transfer of heat from a combustible fuel element or heat source to a tobacco-containing aerosol-generating substrate. During smoking, volatile compounds are released from the aerosol-generating substrate by heat transfer from the heat source and entrained in air drawn through the smoking article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.

[0004] Typically, aerosol-generating articles in which tobacco is heated rather than combusted further comprise one or more elements paired with the aerosol-generating substrate. For example, aerosol-generating articles have been proposed which include a rod of aerosolgenerating substrate and one or more of a support element adapted to impart increased structural strength to the aerosol-generating article, an aerosol-cooling element configured to lower the temperature of the aerosol prior to the aerosol reaching a mouth end of the aerosolgenerating article, and a mouthpiece element.

[0005] It is common to produce aerosol-generating articles in which the aerosol-generating substrate is formed from a cylindrical rod of a tobacco material, such as cut filler or homogenised tobacco material. However, such cylindrical rods of tobacco material have not been found to provide optimal aerosol generation when heated, rather than combusted. A rod of cut filler will typically have a relatively high density and a relatively low porosity, due to the way in which the tobacco material is compacted during manufacture. This can present challenges for the uniform heating of the tobacco material and in fact, research has shown that a significant proportion of the cylindrical rod may not be sufficiently heated to form an aerosol during use. This proportion of the rod is therefore effectively wasted. Furthermore, the fixed size and shape of the cylindrical rod of tobacco material provides little flexibility for the aerosol-generating substrate to be adapted for use in new, more efficient designs of aerosol-generating article and aerosol-generating device.

[0006] It would be desirable to provide a novel substrate for a heated aerosol-generating article, which can achieve a more efficient generation of aerosol and which provides an improved experience for the consumer. It would be particularly desirable to provide such a novel substrate which offers more flexibility to be used in different shapes and forms, such that it can be adapted for use with a wider variety of aerosol-generating articles and devices.

[0007] According to the present disclosure, there is provided an aerosol-generating substrate for use in an aerosol-generating article or system. The aerosol-generating substrate may comprise at least 50 percent by weight of plant particles, on a dry weight basis. The aerosolgenerating substrate may comprise at least 10 percent by weight of aerosol former, on a dry weight basis. The aerosol-generating substrate may comprise one or more hydrocolloid binders, wherein the total amount of hydrocolloid binder is less than or equal to 5 percent by weight of the aerosol-generating substrate, on a dry weight basis. The weight ratio of plant particles to aerosol former in the aerosol-generating substrate may be at least 2.5. The aerosol-generating substrate may be in the form of a plurality of beads or granules.

[0008] According to the present invention there is provided an aerosol-generating substrate for use in an aerosol-generating article or system, the aerosol-generating substrate comprising: at least 50 percent by weight of plant particles, on a dry weight basis; at least 10 percent by weight of aerosol former, on a dry weight basis; and one or more hydrocolloid binders, wherein the total amount of hydrocolloid binder is less than or equal to 5 percent by weight of the aerosol-generating substrate, on a dry weight basis. The weight ratio of plant particles to aerosol former in the aerosol-generating substrate is at least 2.5. The aerosolgenerating substrate is in the form of a plurality of beads or granules.

[0009] According to the present invention there is also provided an aerosol-generating article comprising an aerosol-generating substrate according to the invention, as defined above.

[0010] According to the present disclosure, there is further provided a method of producing an aerosol-generating substrate according to the present disclosure, as defined above. The method may comprise the step of: forming a mixture of plant particles and aerosol former. The method may comprise the step of: mixing the combined plant particles and aerosol former with a binder solution comprising one or more hydrocolloid binders to form a dough. The method may comprise the step of: forming a plurality of beads or granules from the dough.

[0011] According to the present invention there is provided a method of producing an aerosolgenerating substrate according to the present invention, as defined above, the method comprising the steps of: forming a mixture of plant particles and aerosol former; mixing the combined plant particles and aerosol former with a binder solution comprising one or more hydrocolloid binders to form a dough; and forming a plurality of beads or granules from the dough.

[0012] As used herein, the term “aerosol-generating article” refers to an aerosol-generating article for producing an aerosol comprising an aerosol-generating substrate that is intended to be heated rather than combusted in order to release volatile compounds that can form an aerosol. As used herein, the term “aerosol-generating substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol.

[0013] As used herein, the term “granule” refers to a discrete, solid particle formed of the aerosol-generating substrate as defined above. The granule may have a regular or irregular shape.

[0014] As used herein, the term “bead” refers to a discrete, solid particle formed of the aerosolgenerating substrate as defined above and which has a rounded, typically spherical, form.

[0015] The present invention provides a novel and improved form of aerosol-generating substrate for an aerosol-generating article. The aerosol-generating substrate is in the form of a plurality of beads or granules which are formed of a material comprising plant particles, aerosol former and hydrocolloid binder. The combination of plant particles with aerosol former in the relative proportion defined above and with a relatively low amount of hydrocolloid binder has been found to provide an aerosol-generating substrate that can advantageously be formed stably into beads or granules, which retain their shape and can be used directly in an aerosol-generating article. In particular, the consistency and stability of the aerosol-generating substrate used to form the beads or granules enables the beads or granules to be used without the need for an additional coating layer. This simplifies the production process and additionally optimises the release of aerosol from the beads or granules upon heating.

[0016] The granular or beaded form of the aerosol-generating substrate enables it to be used in a wide variety of different types of aerosol-generating article, since the size and number of the beads or granules can be readily adapted to suit the space into which they are incorporated. The aerosol-generating substrate therefore offers improved flexibility and versatility. The aerosol-generating substrate finds particular application in planar or flat aerosol-generating articles, which offer more efficient heating and generation of aerosol due to the flat structure of the aerosol-generating substrate.

[0017] The provision of an aerosol-generating substrate in the form of a plurality of beads or granules also advantageously provides a substrate with a high surface to volume ratio, which optimises release of aerosol from the substrate upon heating.

[0018] Furthermore, aerosol-generating substrates of the present invention comprising tobacco particles have surprisingly been found to provide a significant improvement in the consistency of the nicotine to aerosol former ratio in the aerosol generated upon heating compared to known substrates comprising a rod of tobacco material, as described above. In particular, the aerosol-generating substrate of the present invention can provide a more consistent nicotine to aerosol former ratio in the aerosol per puff across the full duration of heating. This provides the consumer with an optimised sensory experience.

[0019] The aerosol-generating substrate according to the invention can be advantageously produced using known apparatus and methods, with relatively minor modifications. The aerosol-generating substrate can additionally be produced using relatively low amounts of water compared to processes for making other substrates such as homogenised tobacco material, which reduces the time and energy requirements, as well as reducing the environmental impact.

[0020] The aerosol-generating substrate comprises at least 50 percent by weight of plant particles, on a dry weight basis. Preferably, the aerosol-generating substrate comprises at least 60 percent by weight of plant particles, more preferably at least 65 percent by weight of plant particles, more preferably at least 70 percent by weight of plant particles, more preferably at least 75 percent by weight of plant particles, on a dry weight basis.

[0021] Preferably, the aerosol-generating substrate comprises less than or equal to 95 percent by weight of plant particles, more preferably less than or equal to 90 percent by weight of plant particles, more preferably less than or equal to 85 percent by weight of plant particles, on a dry weight basis.

[0022] For example, the aerosol-generating substrate may comprise between 50 percent and 95 percent by weight of plant particles, or between 60 percent and 95 percent by weight of plant particles, or between 65 percent and 95 percent by weight of plant particles, or between 70 percent and 95 percent by weight of plant particles, on a dry weight basis.

[0023] For example, the aerosol-generating substrate may comprise between 50 percent and 90 percent by weight of plant particles, or between 60 percent and 90 percent by weight of plant particles, or between 65 percent and 90 percent by weight of plant particles, or between 70 percent and 90 percent by weight of plant particles, on a dry weight basis.

[0024] For example, the aerosol-generating substrate may comprise between 50 percent and 85 percent by weight of plant particles, or between 60 percent and 85 percent by weight of plant particles, or between 65 percent and 85 percent by weight of plant particles, or between 70 percent and 85 percent by weight of plant particles, on a dry weight basis.

[0025] The plant particles therefore constitute the main component of the aerosol-generating substrate. By adjusting the amount of plant particles in the aerosol-generating substrate it may be advantageously possible to adjust the viscosity and density of the aerosol-generating substrate. Furthermore, by adjusting the amount of plant particles in the aerosol-generating substrate, as well as the relative proportion of the plant particles to the aerosol former, it may be possible to tune the delivery of certain compounds, such as flavour compounds, into the aerosol generated form the aerosol-generating substrate upon heating.

[0026] The plant particles may comprise tobacco particles. With reference to the present invention, the term “tobacco” describes any plant member of the genus Nicotiana. The tobacco particles may include tobacco material from one or more of Bright tobacco, dark tobacco, aromatic tobacco and filler tobacco. In certain embodiments of the invention, the plant particles may consist of tobacco particles.

[0027] Alternatively or in addition to tobacco particles, the plant particles may comprise nontobacco particles. For example, the plant particles may comprise one or more of: tea, coffee, star anise, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

[0028] In certain embodiments, the plant particles may comprise a combination of tobacco particles and non-tobacco particles. In alternative embodiments, the plant particles may be substantially free from tobacco material such that the aerosol-generating substrate is tobacco free.

[0029] The plant particles may have an average particle size of at least 25 microns. Preferably, the plant particles have an average particle size of at least 30 microns. More preferably, the plant particles have an average particle size of at least 35 microns. Even more preferably, the plant particles have an average particle size of at least 40 microns.

[0030] Use of plant particles having an average particle size of 25 microns or more may help control how easily the tobacco particles may be dispersed and kept in suspension within the aerosol former, which helps in providing an homogenous distribution of plant particles throughout the aerosol-generating substrate.

[0031] The plant particles may have an average size of less than or equal to 250 microns. Preferably, the plant particles have an average size of less than or equal to 200 microns. More preferably, the plant particles have an average size of less than or equal to 180 microns. Even more preferably, the plant particles have an average size of less than or equal to 160 microns. Most preferably, the plant particles have an average size of less than or equal to 140 microns.

[0032] In some embodiments, the plant particles have an average size of from 30 microns to 200 microns, preferably from 35 microns to 200 microns, more preferably from 40 microns to 200 microns. In other embodiments, the plant particles have an average size of from 30 microns to 180 microns, preferably from 35 microns to 180 microns, more preferably from 40 microns to 180 microns. In further embodiments, the plant particles have an average size of from 30 microns to 160 microns, preferably from 35 microns to 160 microns, more preferably from 40 microns to 160 microns. In yet other embodiments, the plant particles have an average size of from 30 microns to 140 microns, preferably from 35 microns to 140 microns, more preferably from 40 microns to 140 microns.

[0033] Advantageously, using plant particles having an average size within the ranges described above has a beneficial impact on flowability and malleability of the aerosolgenerating substrate, and may also enable some desirable control over porosity of the formed aerosol-generating substrate, which helps in release of the aerosol species during use. The plant particles may have a D90 value of less than or equal to 300 microns. This expression means that 90 percent of plant particles in the aerosol-generating substrate have a size of less than or equal to 300 microns. For a population of particles, the D90 value may be determined by analysing the particle size distribution. In more detail, looking at a particle size distribution curve, the D90 value can be determined by identifying the point on the curve below which 90 percent of the particles fall.

[0034] Preferably, the plant particles have a D90 value of less than or equal to 275 microns. More preferably, the plant particles have a D90 value of less than or equal to 250 microns. Even more preferably, the plant particles have a D90 value of less than or equal to 200 microns.

[0035] The plant particles may have a D90 value of at least 35 microns. Preferably, the plant particles have a D90 value of at least 40 microns. More preferably, the plant particles have a D90 value of at least 45 microns. Even more preferably, the plant particles have a D90 value of at least 50 microns.

[0036] The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions.

[0037] Using plant particles having a D90 value falling within the ranges described above has the benefit that a regular particle distribution is achieved in the aerosol-generating substrate. This may facilitate controlling the porosity of the aerosol-generating substrate, which helps in release of the aerosol during use. Additionally, this helps ensure that a consistent aerosol can be generated from the aerosol-generating substrate upon heating.

[0038] Where the aerosol-generating substrate comprises plant particles from two or more different plants, the plant particles from each plant may have a different average size and particle size distribution to the plant particles from the other plant or plants. For example, where the aerosol-generating substrate comprises tobacco particles and non-tobacco particles, the D90 value of the non-tobacco particles may be higher than the D90 value of the tobacco particles.

[0039] Preferably, the aerosol-generating substrate comprises tobacco particles having a D90 value of between 35 microns and 100 microns, or between 40 microns and 80 microns, or between 50 microns and 70 microns.

[0040] Alternatively or in addition, the aerosol-generating substrate preferably comprises non- tobacco particles having a D90 value of between 50 microns and 250 microns, or between 75 microns and 200 microns, or between 100 microns and 200 microns, or between 100 microns and 150 microns.

[0041] Preferably, the plant particles are substantially homogeneously distributed through the aerosol-generating substrate. According to the present invention, the weight ratio of plant particles to aerosol former is at least 2.5. Preferably, the weight ratio of plant particles to aerosol former is at least 3, more preferably at least 3.5. This relatively high ratio of solid plant particles to liquid aerosol former ensures that the beads or granules can be formed with the desired consistency, which balances the need for structural stability with the desire to optimise release of aerosol from the aerosol-generating substrate upon heating.

[0042] The weight ratio of plant particles to aerosol former is preferably less than or equal to 5, more preferably less than or equal to 4.5.

[0043] The aerosol-generating substrate comprises at least 10 percent by weight of aerosol former, on a dry weight basis. Preferably, the aerosol-generating substrate comprises at least 12 percent by weight of aerosol former, more preferably at least 15 percent by weight of aerosol former, more preferably at least 17 percent by weight of aerosol former, more preferably at least 20 percent by weight of aerosol former, on a dry weight basis.

[0044] The aerosol-generating substrate preferably comprises less than or equal to 40 percent by weight of aerosol former, more preferably less than or equal to 35 percent by weight of aerosol former, more preferably less than or equal to 30 percent by weight of aerosol former, more preferably less than 25 percent by weight of aerosol former, on a dry weight basis.

[0045] For example, the aerosol-generating substrate may comprise between 10 percent and 40 percent by weight of aerosol former, or between 12 percent and 40 percent by weight of aerosol former, or between 15 percent and 40 percent by weight of aerosol former, or between 17 percent by weight and 40 percent by weight of aerosol former, or between 20 percent and 40 percent by weight of aerosol former, on a dry weight basis.

[0046] For example, the aerosol-generating substrate may comprise between 10 percent and 35 percent by weight of aerosol former, or between 12 percent and 35 percent by weight of aerosol former, or between 15 percent and 35 percent by weight of aerosol former, or between 17 percent by weight and 35 percent by weight of aerosol former, or between 20 percent and 35 percent by weight of aerosol former, on a dry weight basis.

[0047] For example, the aerosol-generating substrate may comprise between 10 percent and 30 percent by weight of aerosol former, or between 12 percent and 30 percent by weight of aerosol former, or between 15 percent and 30 percent by weight of aerosol former, or between 17 percent by weight and 30 percent by weight of aerosol former, or between 20 percent and 30 percent by weight of aerosol former, on a dry weight basis.

[0048] For example, the aerosol-generating substrate may comprise between 10 percent and 25 percent by weight of aerosol former, or between 12 percent and 25 percent by weight of aerosol former, or between 15 percent and 25 percent by weight of aerosol former, or between 17 percent by weight and 25 percent by weight of aerosol former, or between 20 percent and 25 percent by weight of aerosol former, on a dry weight basis. In one preferred embodiment of the invention, the aerosol-generating substrate comprises approximately 24 percent by weight of aerosol former, on a dry weight basis.

[0049] In another preferred embodiment of the invention, the aerosol-generating substrate comprises approximately 18 percent by weight of aerosol former, on a dry weight basis.

[0050] Suitable aerosol formers for use in the manufacture of aerosol-generating substrates according to the present disclosure include, but are not limited to, glycerin, propylene glycol, and mixtures thereof.

[0051] Preferably, the aerosol-generating substrate comprises at least 10 percent by weight of glycerin, more preferably at least 12 percent by weight of glycerin, more preferably at least 15 percent by weight of glycerin, more preferably at least 17 percent by weight of glycerin, more preferably at least 20 percent by weight of glycerin, on a dry weight basis.

[0052] The aerosol-generating substrate preferably comprises less than or equal to 40 percent by weight of glycerin, more preferably less than or equal to 35 percent by weight of glycerin, more preferably less than or equal to 30 percent by weight of glycerin, more preferably less than or equal to 25 percent by weight of glycerin, on a dry weight basis.

[0053] For example, the aerosol-generating substrate may comprise between 10 percent and 40 percent by weight of glycerin, or between 12 percent and 35 percent by weight of glycerin, or between 15 percent and 30 percent by weight of glycerin, or between 17 percent and 25 percent by weight of glycerin, or between 20 percent by weight and 25 percent by weight of glycerin, on a dry weight basis. In one preferred embodiment of the invention, the aerosolgenerating substrate comprises approximately 24 percent by weight of glycerin, on a dry weight basis.

[0054] The aerosol-generating substrate of the present invention further comprises a hydrocolloid binder, which acts to improve the binding of the plant particles in the aerosolgenerating substrate and optimise the structural integrity of the aerosol-generating substrate. According to the invention, the aerosol-generating substrate comprises less than or equal to a maximum of 5 percent by weight of the hydrocolloid binder, on a dry weight basis. This relatively low level of binder has been found to provide the desired physical benefits, without adversely impacting the generation of aerosol from the aerosol-generating substrate.

[0055] Preferably, the total amount of hydrocolloid binder is less than or equal to 4 percent by weight of the aerosol-generating substrate, more preferably less than or equal to 3 percent by weight of the aerosol-generating substrate, more preferably less than or equal to 2 percent by weight of the aerosol-generating substrate, on a dry weight basis.

[0056] Preferably, the total amount of hydrocolloid binder is at least 0.5 percent by weight of the aerosol-generating substrate, more preferably at least 0.6 percent by weight of the aerosolgenerating substrate, more preferably at least 0.7 percent by weight of the aerosol-generating substrate, more preferably at least 0.8 percent by weight of the aerosol-generating substrate, on a dry weight basis.

[0057] For example, the total amount of hydrocolloid binder in the aerosol-generating substrate may be between 0.5 percent and 5 percent by weight, or between 0.5 percent and 4 percent by weight, or between 0.5 percent and 3 percent by weight, or between 0.5 percent and 2 percent by weight, on a dry weight basis.

[0058] For example, the total amount of hydrocolloid binder in the aerosol-generating substrate may be between 0.6 percent and 5 percent by weight, or between 0.6 percent and 4 percent by weight, or between 0.6 percent and 3 percent by weight, or between 0.6 percent and 2 percent by weight, on a dry weight basis.

[0059] For example, the total amount of hydrocolloid binder in the aerosol-generating substrate may be between 0.7 percent and 5 percent by weight, or between 0.7 percent and 4 percent by weight, or between 0.7 percent and 3 percent by weight, or between 0.7 percent and 2 percent by weight, on a dry weight basis.

[0060] For example, the total amount of hydrocolloid binder in the aerosol-generating substrate may be between 0.8 percent and 5 percent by weight, or between 0.8 percent and 4 percent by weight, or between 0.5 percent and 3 percent by weight, or between 0.8 percent and 2 percent by weight, on a dry weight basis.

[0061] Preferably, the weight ratio of plant particles to hydrocolloid binder in the aerosolgenerating substrate is at least 20, more preferably at least 25, more preferably at least 30, more preferably at least 40, more preferably at least 50.

[0062] Preferably, the weight ratio of plant particles to hydrocolloid binder in the aerosolgenerating substrate is less than or equal to 100, more preferably less than or equal to 80.

[0063] Suitable hydrocolloid binders for use in the aerosol-generating substrate of the present invention would be known to the skilled person. The aerosol-generating substrate may be formed with a single hydrocolloid binder, or a combination of two or more hydrocolloid binders.

[0064] Preferably, the one or more hydrocolloid binders are selected from the group consisting of: starch, modified starch, dextrin, alginate, pectin, cellulose, cellulose derivatives (such as carboxymethyl cellulose), agar, carrageenan, gelatin, natural gums (such as tragacanth gum, konjac gum, guar gum or xanthan gum) and combinations thereof.

[0065] Preferably, the one or more hydrocolloid binders are selected from the group consisting of: carboxymethyl cellulose (CMC), hydroxypropyl methyl cellulose (HPMC), guar gum or alginate.

[0066] In certain preferred embodiments of the present invention, the hydrocolloid binder comprises a cellulosic binder. Preferably, the hydrocolloid binder comprises a cellulose derivative. Particularly preferably, the hydrocolloid binder comprises hydroxypropyl methyl cellulose (HPMC). Preferably, the aerosol-generating substrate comprises between 0.5 percent by weight and 2 percent by weight of HPMC, more preferably between 0.5 percent by weight and 1.5 percent by weight of HPMC, on a dry weight basis.

[0067] Preferably, the hydrocolloid binder is selected such that a 2 percent by weight aqueous solution of the hydrocolloid binder has a viscosity of at least 50 cps. Preferably, the hydrocolloid binder is selected such that a 2 percent by weight aqueous solution of the hydrocolloid binder has a viscosity of less than or equal to 5600 cps.

[0068] In preferred embodiments in which the hydrocolloid binder comprises HPMC, a 2 percent by weight aqueous solution of the HPMC has a viscosity of between 50 cps and 5600 cps.

[0069] The term “viscosity” is used herein to denote a measure of a fluid’s internal resistance to deformation under shear stress. In more detail, the term “viscosity” as used herein refers to a fluid’s dynamic viscosity (p). The physical unit for dynamic viscosity in the centimetre gram second system of units (cgs) is the poise (P). 1 poise = 100 centipoise = 0.1 Pa s.

[0070] In more detail, the term “viscosity” denotes the dynamic viscosity of the binder solution as measured at 23 degrees Celsius and at a shear rate of 100 reciprocal seconds (1 / s) during a linear ramp from 1 to 200 reciprocal seconds, using a MCR302 Anton Paar rheometer with a PP25 geometry, the rheometer equipped with a peltier module P-PTD2000 with a VT2 cooling system. As defined above, for the purpose of measuring viscosity of the hydrocolloid binder solution, a solution including 2 percent by weight of the hydrocolloid binder in water is used.

[0071] The use of a hydrocolloid binder which provides a binder solution having a viscosity within these ranges has been advantageously found to optimise both the formulation of the aerosol-generating substrate and the process of production of the aerosol-generating substrate.

[0072] The aerosol-generating substrate according to the present invention may further comprise one or more active agents. For example, the aerosol-generating substrate may comprise exogenous nicotine. The term “exogenous” refers to nicotine that is added to the aerosol-generating substrate as a distinct component from any nicotine that is intrinsically present in the plant particles, for example, where the plant particles comprise tobacco particles. The term “nicotine” encompasses nicotine, a nicotine base or a nicotine salt. In embodiments in which the aerosol-generating substrate comprise a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0073] The aerosol-generating substrate may comprise natural nicotine or synthetic nicotine.

[0074] The total nicotine content of the aerosol-substrate is preferably between 1 percent by weight and 5 percent by weight, more preferably between 1 percent by weight and 3 percent by weight, on a dry weight basis. The total nicotine content corresponds to the total combined amount of intrinsic nicotine which may be present in tobacco material and any exogenous nicotine that is added instead of, or in addition to, tobacco particles.

[0075] Alternatively or in addition, the aerosol-generating substrate of the present invention may comprise one or more cannabinoid compounds selected from the group consisting of: tetrahydrocannabinol (THC), tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), cannabinol (CBN), cannabigerol (CBG), cannabigerol monomethyl ether (CBGM), cannabivarin (CBV), cannabidivarin (CBDV), tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabicyclol (CBL), cannabichromevarin (CBCV), cannabigerovarin (CBGV), cannabielsoin (CBE), cannabicitran (CBT) and combinations thereof. Preferably, the one or more cannabinoid compounds are selected from CBD, THC and a combination thereof. Particularly preferably, the one or more cannabinoid compounds includes CBD.

[0076] Alternatively or in addition, the aerosol-generating substrate of the present invention may further comprise one or more flavourants. Suitable flavourants would be known to the skilled person. The one or more flavourants may comprise one or more of: one or more essential oils such as eugenol, peppermint oil and spearmint oil; one or both of menthol and eugenol; one or both of anethole and linalool.

[0077] The aerosol-generating substrate may further comprise one or more carboxylic acids. Advantageously, where the active agent comprises nicotine, including one or more carboxylic acids in the aerosol-generating substrate may create a nicotine salt. The carboxylic acid may comprise one or more of lactic acid, levulinic acid, benzoic acid, fumaric acid or acetic acid. Preferably, the carboxylic acid is at least one of lactic acid or levulinic acid.

[0078] The aerosol-generating substrate may have a carboxylic acid content of at least 0.5 percent by weight, preferably at least 1 percent by weight, more preferably at least 2 percent by weight, on a dry weight basis.

[0079] The aerosol-generating substrate may have a carboxylic acid content of less than or equal to 10 percent by weight, preferably less than or equal to 8 percent by weight, more preferably less than or equal to 8 precent by weight, on a dry weight basis.

[0080] For example, the aerosol-generating substrate may comprise between about 0.5 percent by weight and about 10 percent by weight of the acid, or between about 1 percent by weight and about 8 percent by weight of the acid, or between about 2 percent by weight and about 6 percent by weight of the acid.

[0081] The aerosol-generating substrate preferably has a total water content of less than or equal to 30 percent by weight, more preferably less than or equal to 20 percent by weight, more preferably less than or equal to 15 percent by weight. The aerosol-generating substrate preferably has a total water content of at least 1 percent by weight, more preferably at least 2 percent by weight, more preferably at least 5 percent by weight.

[0082] For example, the aerosol-generating substrate may have a total water content of between 1 percent and 30 percent by weight, or between 2 percent and 20 percent by weight, or between 5 percent and 15 percent by weight.

[0083] Preferably, the aerosol-generating substrate has a moisture content of less than or equal to 30 percent oven volatiles (OV), more preferably less than or equal to 20 percent oven volatiles (OV), more preferably less than or equal to 15 percent oven volatiles (OV).

[0084] Preferably, the aerosol-generating substrate has a moisture content of at least 1 percent oven volatiles (OV), more preferably at least 2 percent oven volatiles (OV), more preferably at least 5 percent oven volatiles (OV).

[0085] For example, the aerosol-generating substrate may have a moisture content of between 1 percent and 30 percent OV, or between 2 percent and 20 percent OV, or between 5 percent and 15 percent OV.

[0086] The term “percent oven volatiles” (percent OV) is used to refer to the moisture content of a material. It is determined by measuring the percentage weight loss from the material being tested upon drying a sample of the material in an oven at 100 plus or minus 1 degree Celsius (°C) for 3 hours plus or minus 0.5 minutes. In practice, it is assumed that a significant majority of the weight loss from plant material results from the evaporation of moisture. It should be noted that, on an absolute basis, the values of moisture content determined by oven drying may be greater than the results of water content analysis when using a specific method such as ISO 6488 (Karl Fischer method). The difference is sample-type dependent and is due to the loss of volatile materials other than water, (for example, aerosol former) from the tested material during oven drying.

[0087] As discussed above, the beads or granules of the aerosol-generating substrate of the present invention can advantageously be used without the need for an outer coating layer. However, in some embodiments it may be beneficial to provide an aerosol-generating substrate in which the plurality of beads or granules are at least partially coated, for example, with a powder.

[0088] Preferably, the plurality of beads or granules are at least partially coated with a powder. For examples, the plurality of beads or granules may be at least partially coated with tobacco powder. Alternatively or in addition, the plurality of beads or granules may be at least partially coated with a cellulosic material, for example microcrystalline cellulose (MCC).

[0089] The provision of a powder coating may advantageously prevent the adhesion of the beads or granules to each other, which may facilitate the handling of the aerosol-generating substrate, for example, during production of aerosol-generating articles incorporating the aerosol-generating substrate. In addition, the powder coating may provide a moisture barrier to protect the aerosol-generating substrate from environmental moisture.

[0090] The aerosol-generating substrate preferably has a density of at least 0.75 grams per cubic centimetre, more preferably at least 0.8 grams per cubic centimetre, more preferably at least 0.9 grams per cubic centimetre, more preferably at least 1 gram per cubic centimetre, more preferably at least 1.1 grams per cubic centimetre, more preferably at least 1.2 grams per cubic centimetre.

[0091] The aerosol-generating substrate preferably has a density of less than or equal to 2 grams per cubic centimetre, more preferably less than or equal to 1.95 grams per cubic centimetre, more preferably less than or equal to 1.9 grams per cubic centimetre, more preferably less than or equal to 1 .85 grams per cubic centimetre, more preferably less than or equal to 1 .8 grams per cubic centimetre.

[0092] For example, the density of the aerosol-generating substrate may be between 0.75 grams per cubic centimetre and 2 grams per cubic centimetre, or between 0.75 gram per cubic centimetre and 1.95 grams per cubic centimetre, or between 0.75 grams per cubic centimetre and 1.9 grams per cubic centimetre, or between 0.75 grams per cubic centimetre and 1.85 grams per cubic centimetre, or between 0.75 grams and 1.8 grams per cubic centimetre.

[0093] For example, the density of the aerosol-generating substrate may be between 0.8 grams per cubic centimetre and 2 grams per cubic centimetre, or between 0.8 gram per cubic centimetre and 1.95 grams per cubic centimetre, or between 0.8 grams per cubic centimetre and 1.9 grams per cubic centimetre, or between 0.8 grams per cubic centimetre and 1.85 grams per cubic centimetre, or between 0.8 grams and 1.8 grams per cubic centimetre.

[0094] For example, the density of the aerosol-generating substrate may be between 0.9 grams per cubic centimetre and 2 grams per cubic centimetre, or between 0.9 gram per cubic centimetre and 1.95 grams per cubic centimetre, or between 0.9 grams per cubic centimetre and 1.9 grams per cubic centimetre, or between 0.9 grams per cubic centimetre and 1.85 grams per cubic centimetre, or between 0.9 grams and 1.8 grams per cubic centimetre.

[0095] For example, the density of the aerosol-generating substrate may be between 1 gram per cubic centimetre and 2 grams per cubic centimetre, or between 1 gram per cubic centimetre and 1.95 grams per cubic centimetre, or between 1 gram per cubic centimetre and 1.9 grams per cubic centimetre, or between 1 gram per cubic centimetre and 1.85 grams per cubic centimetre, or between 1 gram and 1.8 grams per cubic centimetre.

[0096] For example, the density of the aerosol-generating substrate may be between 1.1 grams per cubic centimetre and 2 grams per cubic centimetre, or between 1.1 grams per cubic centimetre and 1.95 grams per cubic centimetre, or between 1.1 grams per cubic centimetre and 1.9 grams per cubic centimetre, or between 1.1 grams per cubic centimetre and 1.85 grams per cubic centimetre, or between 1.1 grams and 1.8 grams per cubic centimetre. For example, the density of the aerosol-generating substrate may be between 1.2 grams per cubic centimetre and 2 grams per cubic centimetre, or between 1.2 grams per cubic centimetre and 1.95 grams per cubic centimetre, or between 1.2 grams per cubic centimetre and 1.9 grams per cubic centimetre, or between 1.2 grams per cubic centimetre and 1.85 grams per cubic centimetre, or between 1.2 grams and 1.8 grams per cubic centimetre.

[0097] The density of the aerosol-generating substrate may be measured using a density meter, such as a Density meter Excellence available from Mettler Toledo®. Using such a meter, a bead of granule of aerosol-generating substrate is first weighed to determine the weight. The bead or granule is then placed in a container of sunflower oil (2-3 cm in depth) and allowed to sink. The density of the sunflower oil is inputted into the meter (0.9188) and the density value of the bead is then calculated by the meter. This calculation is based on Archimedes principle and uses the following formula, in which the object is the bead or granule of aerosol-generating substrate and the fluid is the sunflower oil:

[0098] The size of the beads or granules may be adapted depending upon the desired use of the aerosol-generating substrate. The mean weight of the plurality of beads or granules is preferably at least 0.6 mg, more preferably at least 2 mg, more preferably at least 10 mg, more preferably at least 20 mg. Preferably, the mean weight of the plurality of beads or granules is less than or equal to 80 mg, more preferably less than or equal to 60 mg, more preferably less than or equal to 40 mg.

[0099] For example, the mean weight of the plurality of beads or granules may be between 0.6 mg and 80 mg, or between 2 mg and 60 mg, or between 10 mg and 40 mg, or between 20 mg and 40 mg.

[0100] The mean weight of the plurality of beads or granules is defined as the total weight of the plurality of beads of granules, divided by the total number of beads or granules. The mean weight therefore indicates the weight of an individual bead or granule.

[0101] The total weight of the plurality of beads or granules is preferably at least 50 mg, more preferably at least 100 mg, more preferably at least 125 mg, more preferably at least 150 mg. Preferably, the total weight of the plurality of beads or granules is less than or equal to 350 mg, more preferably less than or equal to 300 mg, more preferably less than or equal to 250 mg, more preferably less than or equal to 200 mg.

[0102] For example, the total weight of the plurality of beads or granules may be between 50 mg and 350 mg, or between 100 mg and 300 mg, or between 125 mg and 250 mg, or between 150 mg and 200 mg. The bulk density of the plurality of beads or granules is preferably at least 200 mg per cubic centimetre, more preferably at least 210 mg per cubic centimetre, more preferably at least 225 mg per cubic centimetre, more preferably at least 240 mg per cubic centimetre more preferably at least 250 mg per cubic centimetre. Preferably, the bulk density of the plurality of beads or granules is less than or equal to 500 mg per cubic centimetre, more preferably less than or equal to 485 mg per cubic centimetre, more preferably less than or equal to 475 mg per cubic centimetre, more preferably less than or equal to 465 mg per cubic centimetre, more preferably less than or equal to 450 mg per cubic centimetre.

[0103] For example, the bulk density of the plurality of beads or granules may be between 200 mg per cubic centimetre and 500 mg per cubic centimetre, or between 210 mg per cubic centimetre and 485 mg per cubic centimetre, or between 225 mg per cubic centimetre and 475 mg per cubic centimetre, or between 240 mg per cubic centimetre and 465 mg per cubic centimetre, or between 250 mg per cubic centimetre and 450 mg per cubic centimetre.

[0104] The bulk density of the plurality of beads or granules is defined as the total weight of the plurality of beads or granules, divided by the volume of the space occupied by the plurality of beads or granules.

[0105] The mean surface area of the plurality of beads or granules is preferably at least 3 square millimetres, more preferably at least 5 square millimetres, more preferably at least 8 square millimetres, more preferably at least 10 square millimetres, more preferably at least 12 square millimetres, more preferably at least 15 square millimetres, more preferably at least 18 square millimetres, more preferably at least 20 square millimetres. Preferably, the mean surface area of the plurality of beads is less than or equal to 80 square millimetres, more preferably less than or equal to 75 square millimetres, more preferably less than or equal to 70 square millimetres, more preferably less than or equal to 65 square millimetres, more preferably less than or equal to 60 square millimetres, more preferably less than or equal to 50 square millimetres, more preferably less than or equal to 40 square millimetres.

[0106] For example, the plurality of beads or granules may have a mean surface area of between 3 square millimetres and 80 square millimetres, or between 5 square millimetres and 75 square millimetres, or between 8 square millimetres and 70 square millimetres, or between 10 square millimetres and 65 square millimetres, or between 12 square millimetres and 60 square millimetres, or between 15 square millimetres and 50 square millimetres, or between 18 square millimetres and 40 square millimetres, or between 20 square millimetres and 40 square millimetres.

[0107] The mean surface area of the plurality of beads or granules is defined as the total surface area of the plurality of beads or granules divided by the total number of beads or granules. The total surface area of the plurality of beads or granules is preferably at least 120 square millimetres, more preferably at least 200 square millimetres, more preferably at least 300 square millimetres. Preferably, the total surface area of the plurality of beads is less than or equal to 650 square millimetres, more preferably less than or equal to 500 square millimetres, more preferably less than or equal to 400 square millimetres.

[0108] For example, the plurality of beads or granules may have a total surface area of between 120 square millimetres and 650 square millimetres, or between 200 square millimetres and 500 square millimetres, or between 300 square millimetres and 400 square millimetres.

[0109] The mean diameter of the plurality of beads or granules is preferably at least 0.5 millimetres, more preferably at least 0.75 millimetre, more preferably at least 1 millimetre, more preferably at least 1 .5 millimetres. Preferably, the mean diameter of the plurality of beads or granules is less than or equal to 10 millimetres, more preferably less than or equal to 8 millimetres, more preferably less than or equal to 6 millimetres, more preferably less than or equal to 4 millimetres, more preferably less than or equal to 2.5 millimetres.

[0110] For example, the mean diameter of the plurality of beads or granules may be between 0.5 millimetres and 10 millimetres, or between 0.5 millimetres and 8 millimetres, or between 0.5 millimetres and 6 millimetres, or between 0.5 millimetres and 4 millimetres, or between 0.5 millimetres and 2.5 millimetres, or between 0.75 millimetres and 10 millimetres, or between 0.75 millimetres and 8 millimetres, or between 0.75 millimetres and 6 millimetres, or between 0.75 millimetres and 4 millimetres, or between 0.75 millimetres and 2.5 millimetres, or between 1 millimetres and 10 millimetres, or between 1 millimetres and 8 millimetres, or between 1 millimetres and 6 millimetres, or between 1 millimetres and 4 millimetres, or between 1 millimetres and 2.5 millimetres, or between 1 .5 millimetres and 10 millimetres, or between 1.5 millimetres and 8 millimetres, or between 1.5 millimetres and 6 millimetres, or between 1.5 millimetres and 4 millimetres or between 1.5 millimetres and 2.5 millimetres.

[0111] The mean diameter of the plurality of beads or granules is defined as the sum of the diameters of the plurality of beads or granules, divided by the total number of beads or granules. For the avoidance of doubt, as used herein with reference to the present invention, the term ‘diameter’ is used to describe the maximum dimension of a bead or granule. For beads having a substantially circular cross-section or a substantially spherical shape, the term diameter refers to the diameter of the circular cross-section or the diameter of the sphere respectively. However, where the beads or granules have a shape which is not substantially spherical, the term ‘diameter’ is used to refer to the maximum dimension of the bead or granule.

[0112] The beads or granules forming the aerosol-generating substrate may have any suitable shape. Where the aerosol-generating substrate is in the form of a plurality of granules, the granules may have a regular shape, such as cylindrical, or an irregular shape. The granules may be the same shape as each other, or the plurality of granules may alternatively comprise granules of different shapes.

[0113] Preferably, the granules have a length that is greater than their width, such that the granules are elongate in form, for example, cylindrical, rectangular cuboidal or in the form of a filament.

[0114] The shape of the granules has been found to affect the rate of release of active agent, such as nicotine, from the granules. For example, the present inventors have surprisingly found that the higher the ratio between the length and the width of the granules, the slower the rate of release of the active agent. The shape of the granules can therefore be adapted to provide the desired rate of release of the active agent. The plurality of granules may comprise a combination of granules with different shapes or sizes (or both). This may advantageously provide greater control over the release of an active agent from the plurality of granules.

[0115] Preferably, the aerosol-generating substrate is in the form of a plurality of rounded beads, such as spherical, ovoid or ellipsoid beads. In particularly preferred embodiments of the present invention, the aerosol-generating substrate is in the form of a plurality of substantially spherical beads of the aerosol-generating substrate.

[0116] The plurality of beads may comprise a combination of beads with different diameters. As described above in relation to the granules, the bead size may affect the release profile of the active agent from the beads and the use of a combination of bead sizes may advantageously provide greater control over the release of an active agent from the beads.

[0117] In certain embodiments of the present invention, a plurality of beads may be combined with a plurality of granules, to provide a combination of different size and shape elements.

[0118] As defined above, the present invention further provides a method for the production of an aerosol-generating substrate according to the invention, as defined above. The method according to the present invention comprises the steps of: forming a mixture of plant particles and aerosol former; mixing the combined plant particles and aerosol former with a binder solution comprising one or more hydrocolloid binders to form a dough; forming a plurality of beads or granules from the dough.

[0119] The plant particles may comprise tobacco or non-tobacco particles, or a combination thereof, as described above.

[0120] The binder solution is preferably a solution of the binder in water or glycerin, or a combination thereof.

[0121] The step of forming the plurality of beads or granules from the dough may be carried out using any suitable means, including for example extrusion, (such as high shear extrusion), spray granulation, or moulding. Preferably, the step of forming the plurality of beads or granules comprise extruding the dough to form a plurality of discrete elements. For preferred embodiments in which the aerosol-generating substrate comprises a plurality of spherical beads, the step of forming the plurality of beads may further comprise the step of spheronizing the extruded discrete elements to form spherical beads.

[0122] A suitable apparatus for forming the discrete elements by extrusion is the Caleva® Model 20 Extruder. A suitable apparatus for carrying out the spheronization of the discrete elements is the Caleva® Multi Bowl Spheronizer 250.

[0123] Methods according to the present invention may further comprise a step of drying the plurality of beads or granules to a desired water content. The drying step may be carried out using any suitable means, including but not limited to heating and lyophilisation.

[0124] Methods according to the present invention may further comprise a step of applying a powder coating to the plurality of beads or granules. As described above, the powder coating may comprise at least one of tobacco powder, or a cellulosic powder such as microcrystalline cellulose (MCC).

[0125] Advantageously, methods according to the present invention use a relatively low amount of water through the production of a dough, rather than a slurry, including plant particles. The amount of water that needs to be evaporated from the substrate during the production method is therefore relatively low. This reduces the duration and energy requirements for the drying step or steps such that the aerosol-generating substrate can be produced in a more sustainable manner than alternative aerosol-generating substrates.

[0126] Aerosol-generating substrates according to the present invention may be used in a wide variety of different aerosol-generating articles. As defined below, the present invention provides an aerosol-generating article comprising an aerosol-generating substrate according to the present invention, as described above.

[0127] The aerosol-generating substrate may be combined with one or more elements upstream or downstream of the aerosol-generating substrate.

[0128] Aerosol-generating articles according to the invention may comprise at least 2 beads or granules of aerosol-generating substrate, more preferably at least 5 beads or granules of aerosol-generating substrate, more preferably at least 10 beads or granules of aerosolgenerating substrate, more preferably at least 20 beads or granules of aerosol-generating substrate, more preferably at least 30 beads or granules of aerosol-generating substrate, more preferably at least 40 beads or granules of aerosol-generating substrate,

[0129] Aerosol-generating articles according to the invention may comprise less than or equal to 200 beads or granules of aerosol-generating substrate, more preferably less than or equal to 100 beads of granules of aerosol-generating substrate, more preferably less than or equal to 75 beads of granules of aerosol-generating substrate, more preferably less than or equal to 50 beads of granules of aerosol-generating substrate.

[0130] For example, aerosol-generating articles according to the invention may comprise between 2 beads and 200 beads or granules of aerosol-generating substrate, or between 5 beads and 200 beads or granules of aerosol-generating substrate, or between 10 beads and 100 beads or granules of aerosol-generating substrate, or between 20 beads and 75 beads or granules of aerosol-generating substrate, or between 30 beads and 50 beads or granules of aerosol-generating substrate, or between 40 beads and 50 beads or granules of aerosolgenerating substrate.

[0131] An aerosol-generating article according to the present invention may comprise a total weight of at least 50 mg of the beads or granules of aerosol-generating substrate, preferably at least 100 mg of the beads or granules of aerosol-generating substrate, more preferably at least 125 mg of the beads or granules of aerosol-generating substrate, more preferably at least 150 mg of the beads or granules of aerosol-generating substrate. Preferably, the total weight of the plurality of beads or granules in the aerosol-generating article is less than or equal to 350 mg, more preferably less than or equal to 300 mg, more preferably less than or equal to 250 mg, more preferably less than or equal to 200 mg.

[0132] For example, the total weight of the plurality of beads or granules in the aerosolgenerating article may be between 50 mg and 350 mg, or between 100 mg and 300 mg, or between 125 mg and 250 mg, or between 150 mg and 200 mg.

[0133] Preferably, the aerosol-generating article according to the invention is substantially flat, or substantially planar. This means that the article has a relatively large base area relative to the volume of the article. As described above, the aerosol-generating substrate of the present invention has been found to be particularly suitable for use in flat aerosol-generating articles since it can be readily adapted to fill a space within an article having a flat shape with relatively large opposed surfaces. This form optimises heating of the aerosol-generating substrate and the generation of aerosol.

[0134] In certain preferred embodiments of the present invention, the aerosol-generating article comprises: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity; an air inlet and an air outlet; and an airflow passage extending between the air inlet and the air outlet through the cavity. The plurality of beads or granules of aerosol-generating substrate are positioned between the first planar external surface and the second planar external surface, typically within the cavity.

[0135] The cavity may have a length of at least 10 millimetres, or at least 12 millimetres. The cavity may have a length of less than or equal to 20 millimetres, or less than or equal to 15 millimetres. For example, the cavity may have a length of between 10 millimetres and 20 millimetres, or between 12 millimetres and 15 millimetres.

[0136] The cavity may have a width of at least 5 millimetres, or at least 6 millimetres. The cavity may have a width of less than or equal to 10 millimetre, or less than or equal to 8 millimetres. For example, the cavity may have a width of between 5 millimetres and 10 millimetres, or between 6 millimetres and 8 millimetres.

[0137] The cavity may have a depth of at least 2 millimetres, or at least 3 millimetres. The cavity may have a depth of less than or equal to 5 millimetres, or less than or equal to 4 millimetres. For example, the cavity may have a depth of between 2 millimetres and 5 millimetres, or between 3 millimetres and 4 millimetres.

[0138] The cavity may have a volume of at least 200 square millimetres, or at least 250 square millimetres. The cavity may have a volume of less than or equal to 400 square millimetres, or less than or equal to 350 square millimetres. For example, the cavity may have a volume of between 200 square millimetres and 400 square millimetres, or between 250 square millimetres and 350 square millimetres.

[0139] In alternative preferred embodiments of the present invention, the aerosol-generating article comprises a container, the container comprising a first wall and a second wall together defining a substrate compartment, wherein the plurality of beads or granules are provided in the substrate compartment.

[0140] The first wall may comprise a different material to the second wall. This provision may advantageously allow the first and second wall to have different properties tailored for different functions. For example, the first and second walls may be configured to have different porosities, different thermal conductivities, or different stiffnesses.

[0141] The first wall may comprise a flexible material, such as a flexible cellulosic material. The second wall may have a higher stiffness than the first wall.

[0142] At least a portion of the first or second wall may be porous.

[0143] The container as defined above may be in the form of a pouch.

[0144] Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0145] EX1. An aerosol-generating substrate for use in an aerosol-generating article or system, the aerosol-generating substrate comprising: plant particles; and aerosol former, wherein the aerosol-generating substrate is in the form of a plurality of beads or granules. EX2. An aerosol-generating substrate for use in an aerosol-generating article or system, the aerosol-generating substrate comprising: plant particles; aerosol former; and one or more hydrocolloid binders, wherein the aerosol-generating substrate is in the form of a plurality of beads or granules.

[0146] EX3. An aerosol-generating substrate according to example EX1 or EX2, wherein the aerosol-generating substrate comprises at least 50 percent by weight of the plant particles, on a dry weight basis.

[0147] EX4. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate comprises at least 60 percent by weight of the plant particles, for example at least 65 percent by weight of the plant particles, for example at least 70 percent by weight of the plant particles, for example at least 75 percent by weight of the plant particles, on a dry weight basis.

[0148] EX5. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate comprises less than or equal to 95 percent by weight of the plant particles, for example less than or equal to 90 percent by weight of the plant particles, for example less than or equal to 85 percent by weight of the plant particles, on a dry weight basis.

[0149] EX6. An aerosol-generating substrate according to any preceding example, wherein the plant particles comprise tobacco particles.

[0150] EX7. An aerosol-generating substrate according to any preceding example, wherein the plant particles comprise non-tobacco particles.

[0151] EX8. An aerosol-generating substrate according to example EX7, wherein the nontobacco particles comprise particles of one or more of: tea, coffee, star anise, lavender, clove, peppermint, chamomile, rosemary, eucalyptus, ginger, dill seed, thyme, oregano and cumin.

[0152] EX9. An aerosol-generating substrate according to any preceding example, wherein the plant particles have an average particle size of at least 30 microns, for example at least 35 microns, for example at least 40 microns, for example at least 45 microns.

[0153] EX10. An aerosol-generating substrate according to any preceding example, wherein the plant particles have a D90 value of less than or equal to 300 microns, for example less than or equal to 275 microns, for example less than or equal to 250 microns, for example less than or equal to 200 microns.

[0154] EX11 . An aerosol-generating substrate according to any preceding example, wherein the plant particles comprise tobacco particles having a D90 value of between 50 microns and 70 microns. EX12. An aerosol-generating substrate according to any preceding example, wherein the plant particles comprise non-tobacco particles having a D90 value of between 100 microns and 200 microns.

[0155] EX13. An aerosol-generating substrate according to any preceding example, wherein the plant particles are substantially homogeneously distributed through the aerosol-generating substrate.

[0156] EX14. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to aerosol former is at least 2.5.

[0157] EX15. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to aerosol former is at least 3, for example at least 3.5.

[0158] EX16. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to aerosol former is less than or equal to 5, for example less than or equal to 4.5.

[0159] EX17. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to hydrocolloid binder is at least 20, for example at least 25, for example at least 30, for example at least 40, for example at least 50.

[0160] EX18. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to hydrocolloid binder is less than or equal to 100, for example less than or equal to 80.

[0161] EX19. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate comprises at least 10 percent by weight of aerosol former, for example at least 15 percent by weight of aerosol former, for example at least 20 percent by weight of aerosol former, on a dry weight basis.

[0162] EX20. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate comprises less than or equal to 40 percent by weight of aerosol former, for example less than or equal to 35 percent by weight of aerosol former, for example less than or equal to 30 percent by weight of aerosol former, on a dry weight basis.

[0163] EX21. An aerosol-generating substrate according to any preceding example, wherein the aerosol former comprises glycerin, propylene glycol or a combination thereof.

[0164] EX22. An aerosol-generating substrate according to any preceding example, wherein the total amount of hydrocolloid binder is less than or equal to 5 percent by weight of the aerosol-generating substrate, on a dry weight basis.

[0165] EX23. An aerosol-generating substrate according to any preceding example, wherein the total amount of hydrocolloid binder is less than or equal to 4 percent by weight of the aerosol-generating substrate, for example less than or equal to 3 percent by weight of the aerosol-generating substrate, for example less than or equal to 2 percent by weight of the aerosol-generating substrate, on a dry weight basis. EX24. An aerosol-generating substrate according to any preceding example, wherein the total amount of hydrocolloid binder is at least 0.5 percent by weight, for example at least 0.6 percent by weight, for example at least 0.7 percent by weight, for example at least 0.8 percent by weight, on a dry weight basis.

[0166] EX25. An aerosol-generating substrate according to any preceding example, wherein the hydrocolloid binder comprises a cellulosic binder.

[0167] EX26. An aerosol-generating substrate according to example EX25, wherein the cellulosic binder comprises a cellulose derivative.

[0168] EX27. An aerosol-generating substrate according to example EX25 or EX26, wherein the cellulosic binder comprises hydroxypropyl methyl cellulose (HPMC).

[0169] EX28. An aerosol-generating substrate according to example EX27, wherein the aerosol-generating substrate comprises between 0.5 percent by weight and 2 percent by weight of HPMC.

[0170] EX29. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to hydrocolloid binder is at least 20, for example at least 25, for example at least 30, for example at least 40, for example at least 50.

[0171] EX30. An aerosol-generating substrate according to any preceding example, wherein the weight ratio of plant particles to hydrocolloid binder is less than or equal to 100, for example less than or equal to 80.

[0172] EX31 . An aerosol-generating substrate according to any preceding example, further comprising an active agent, for example exogenous nicotine.

[0173] EX32. An aerosol-generating substrate according to any preceding example, further comprising a flavourant.

[0174] EX33. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate further comprises one or more carboxylic acids.

[0175] EX34. An aerosol-generating substrate according to example EX28, wherein the aerosol-generating substrate comprises between 0.5 percent and 10 percent by weight of carboxylic acid, for example between 1 percent and 8 percent by weight of carboxylic acid, for example between 2 percent and 6 percent by weight of carboxylic acid, on a dry weight basis.

[0176] EX35. An aerosol-generating substrate according to any preceding example, wherein the total water content of the aerosol-generating substrate is less than or equal to 30 percent by weight, for example less than or equal to 20 percent by weight, for example less than or equal to 15 percent by weight.

[0177] EX36. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate has a moisture content of less than or equal to 30 percent oven volatiles, for example less than or equal to 20 percent oven volatiles, for example less than or equal to 15 percent oven volatiles. EX37. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate has a nicotine content of between 1 percent and 5 percent by weight, for example between 1 percent and 3 percent by weight, on a dry weight basis.

[0178] EX38. An aerosol-generating substrate according to any preceding example, wherein the plurality of beads or granules are at least partially coated with a powder.

[0179] EX39. An aerosol-generating substrate according to example EX38, wherein the powder comprises tobacco powder.

[0180] EX40. An aerosol-generating substrate according to example EX38, wherein the powder comprises a cellulosic powder, for example microcrystalline cellulose (MCC).

[0181] EX41 . An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate has a density of at least 0.75 grams per cubic centimetre, for example at least 1 gram per cubic centimetre, for example at least 1.1 grams per cubic centimetre, for example at least 1 .2 grams per cubic centimetre.

[0182] EX42. An aerosol-generating substrate according to any preceding example, wherein the aerosol-generating substrate has a density of less than or equal to 2 grams per cubic centimetre, for example less than or equal to 1.9 grams per cubic centimetre, for example less than or equal to 1 .8 grams per cubic centimetre.

[0183] EX43. An aerosol-generating substrate according to any preceding example, wherein the mean weight of the plurality of beads or granules is at least 0.6 mg, for example at least 2 mg, for example at least 10 mg, for example at least 20 mg.

[0184] EX44. An aerosol-generating substrate according to any preceding example, wherein the mean weight of the plurality of beads or granules is less than or equal to 80 mg, for example less than or equal to 60 mg, for example less than or equal to 40 mg.

[0185] EX45. An aerosol-generating substrate according to any preceding example, wherein the total weight of the plurality of beads or granules is at least 50 mg, for example at least 100 mg, for example at least 125 mg, for example at least 150 mg.

[0186] EX46. An aerosol-generating substrate according to any preceding example, wherein the total weight of the plurality of beads of granules is less than or equal to 350 mg, for example less than or equal to 300 mg, for example less than or equal to 250 mg.

[0187] EX47. An aerosol-generating substrate according to any preceding example, wherein the bulk density of the plurality of beads or granules is at least 200 mg per cubic centimetre, for example at least 225 mg per cubic centimetre, for example at least 250 mg per cubic centimetre.

[0188] EX48. An aerosol-generating substrate according to any preceding example, wherein the bulk density of the plurality of beads or granules is less than or equal to 500 mg per cubic centimetre, for example less than or equal to 475 mg per cubic centimetre, for example less than or equal to 450 mg per cubic centimetre. EX49. An aerosol-generating substrate according to any preceding example, wherein the mean surface area of the plurality of beads or granules is at least 3 millimetres squared, for example at least 10 millimetres squared, for example at least 20 millimetres squared.

[0189] EX50. An aerosol-generating substrate according to any preceding example, wherein the mean surface area of the plurality of beads or granules is less than or equal to 80 millimetres squared, for example less than or equal to 60 millimetres squared, for example less than or equal to 40 millimetres squared.

[0190] EX51 . An aerosol-generating substrate according to any preceding example, wherein the total surface area of the plurality of beads or granules is at least 120 millimetres squared, for example at least 240 millimetres squared.

[0191] EX52. An aerosol-generating substrate according to any preceding example, wherein the total surface area of the plurality of beads or granules is less than or equal to 650 millimetres squared, for example less than or equal to 500 millimetres squared.

[0192] EX53. An aerosol-generating substrate according to any preceding example, wherein the mean diameter of the plurality of beads or granules is at least 0.5 millimetre, for example at least 1 millimetre, for example at least 1.5 millimetres.

[0193] EX54. An aerosol-generating substrate according to any preceding example, wherein the mean diameter of the plurality of beads or granules is less than or equal to 4 millimetres, for example less than or equal to 3 millimetres, for example less than or equal to 2.5 millimetres.

[0194] EX55. An aerosol-generating substrate according to any preceding example, comprising a plurality of substantially spherical beads.

[0195] EX56. An aerosol-generating article comprising the aerosol-generating substrate according to any preceding example.

[0196] EX57. An aerosol-generating article according to example EX56, wherein the aerosolgenerating article is substantially flat.

[0197] EX58. An aerosol-generating article according to example EX57, the aerosolgenerating article comprising: a first planar external surface; a second planar external surface; a cavity; a frame positioned between the first planar external surface and the second planar external surface, the frame at least partially defining the cavity, wherein the plurality of beads or granules are provided within the cavity between the first planar external surface and the second planar external surface; an air inlet and an air outlet; and an airflow passage extending between the air inlet and the air outlet through the cavity. EX59. An aerosol-generating article according to example EX56, the aerosolgenerating article comprising: a container, the container comprising: a first wall and a second wall together defining a substrate compartment, wherein the plurality of beads or granules are provided in the substrate compartment. EX60. A method of producing an aerosol-generating substrate according to any of the examples EX1 to EX55, the method comprising the steps of: forming a mixture of plant particles and aerosol former; mixing the combined plant particles and aerosol former with a binder solution comprising one or more hydrocolloid binders to form a dough; forming a plurality of beads or granules from the dough.

[0198] EX61 . A method according to example EX60, wherein the step of forming the plurality of beads or granules comprises extruding the dough to form a plurality of discrete elements.

[0199] EX62. A method according to example EX61 , wherein the plurality of discrete elements are spheronized to form a plurality of spherical beads.

[0200] EX63. A method according to any of examples EX60 to EX62, further comprising the step of drying the plurality of beads or granules.

[0201] EX64. A method according to any of examples EX60 to EX63, further comprising the step of applying a powder coating to the plurality of beads or granules, wherein the powder coating comprises at least one of tobacco and cellulose, for example microcrystalline cellulose.

[0202] Examples will now be further described with reference to the figures in which:

[0203] Figure 1 shows a perspective view of an aerosol-generating article according to a first embodiment of the invention;

[0204] Figure 2 shows an exploded perspective view of the aerosol-generating article of Figure 1 ;

[0205] Figure 3 shows a transverse cross-sectional view of the aerosol-generating article of Figure 1 ; and

[0206] Figure 4 shows a schematic cross-sectional view of an aerosol-generating article according to a second embodiment of the invention.

[0207] Figure 1 shows an aerosol-generating article 10 comprising a first planar external layer 24 forming a first planar external surface 21 , a second planar external layer 25 forming a second planar external surface 22, and a frame 50 positioned between the first planar external layer 24 and the second planar external layer 25. The first planar external layer 24 and the second planar external layer 25 may be formed from a non-aerosol forming material, such as paper or card. Alternatively, either of the first planar external layer 24 and the second planar external layer 25 may comprise an aerosol-generating substrate comprising an aerosolgenerating material, for example tobacco. The aerosol-generating article 10 has a length extending in the x-direction, a width extending in the y-direction and a thickness extending in the z-direction. The aerosolgenerating article 10 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 3.1 millimetres.

[0208] The first planar external surface 21 and the second planar external surface 22 extend in the x-direction and the y-direction. That is, the first planar external surface 21 and the second planar external surface 22 extend in the x / y plane. The first planar external surface 21 is positioned parallel to the second planar external surface 22 and the first planar external surface 21 is spaced from the second planar external surface 22 in the z-direction or transverse direction. The distance between the first planar external surface 21 and the second planar external surface 22 in the z-direction or transverse direction corresponds to the thickness of the aerosol-generating article 10.

[0209] The aerosol-generating article 10 is a substantially flat aerosol-generating article or substantially planar aerosol-generating article. In particular, the thickness of the aerosolgenerating article 10 is less than 50 percent of both the length and the width of the aerosolgenerating article. The aerosol-generating article 10 has a generally rectangular cuboid shape and a laminated structure formed by the first planar external layer 24, the frame 50 and the second planar external layer 25. The first planar external layer 24, the frame 50 and the second planar external layer 25 are bonded together with an adhesive, in particular guar gum.

[0210] Figure 2 shows an exploded view of the aerosol-generating article 10 of Figure 1.

[0211] The frame 50 has a length of 30 millimetres, a width of 10 millimetres, and a thickness of 2.7 millimetres. The frame 50 is made from cardboard and defines a frame aperture extending through the thickness of the frame 50. The frame aperture at least partially forms a cavity 30. The cavity 30 has length of 15 millimetres, a width of 7 millimetres, and a depth of 3.3 millimetres. Therefore, the cavity 30 has a volume of about 346.5 cubic millimetres. The cavity 30 is filled with a plurality of beads of aerosol-generating substrate 40 (shown schematically). The beads of aerosol-generating substrate 40 fill the entire volume of the cavity 30 and airflow through the cavity 30 is provided by interstices between adjacent beads. The beads of aerosol-generating substrate 40 will be described in more detail below.

[0212] The first planar external layer 24 and the second planar external layer 25 have a thickness of 200 micrometres and are in physical contact with the frame 50. The first planar external layer 24 and the second planar external layer 25 are bonded to the frame with an adhesive 15. The first planar external layer 24 overlies an end of the cavity 30 and forms a first cavity end wall 31 . The second planar external layer 25 overlies an opposite end of the cavity 30 and forms a second cavity end wall 32. That is, the frame 50, the first planar external layer 24 and the second planar external layer 25 collectively define the cavity 30. The frame 50 comprises a peripheral wall 51 that circumscribes the cavity 30. The peripheral wall 51 has a radial thickness of about 2 millimetres.

[0213] An air inlet (not visible) and an air outlet 12 are defined by, and extend through, the peripheral wall 51 of the frame 50. The air inlet is positioned opposite the air outlet 12, on the opposite wall of the frame 50. The air inlet and the air outlet 12 each have a rectangular crosssection, a width of 2 millimetres, and a thickness of 0.9 millimetres. An airflow passage extends between the air inlet and the air outlet 12 through the cavity 30.

[0214] The beads of aerosol-generating substrate 40 are substantially spherical in shape with a diameter of 1 .5 millimetres and a density of 1.3 grams per cubic centimetre. The total weight of the beads of aerosol-generating substrate 40 in the cavity 30 is approximately 150 mg. The beads are formed of an aerosol-generating substrate comprising plant particles, aerosol former and a hydrocolloid binder. An example of a suitable composition of the aerosolgenerating substrate for forming the beads is provided below.

[0215] Figure 4 shows an aerosol-generating article 100 according to a second embodiment of the invention. The aerosol-generating article 100 comprises a container 110. The container 110 comprises a first wall 111 and a second wall 112 which together define a substrate compartment 113. A plurality of spherical beads 114 of aerosol-generating substrate (shown schematically) are provided in the substrate compartment 113. The substrate compartment 113 has a length of 17 millimetres, a width of 8 millimetres and a depth of 3.5 millimetres.

[0216] The first wall 111 is formed from a non-woven cotton material. The first wall 111 comprises between 85 weight percent and 90 weight percent cellulose, between 7 weight percent and 16 weight percent hemicellulose, and between 1 weight percent and 3 weight percent lignin. The first wall 111 is porous.

[0217] The second wall 112 comprises paper. The second wall 112 has a grammage of about 35 gsm. The second wall is non-porous.

[0218] The second wall 112 may be substantially planar. The second wall 112 has a higher stiffness than the first wall 111. In this way, the first wall 111 may generally form a bag shape which is closed by the second wall 112.

[0219] The first wall 111 and the second wall 112 meet at a contact region 116. The contact region 116 extends around the circumference of the container 110. The contact region 116 has a thickness of 3.5 millimetres. The first wall 111 and the second wall 112 are connected at the contact region 116 by an adhesive to form a sealing region. The adhesive is a polyvinyl alcohol adhesive.

[0220] The first wall 111 and the second wall 112 are thermally stable less than or equal to at least 280 degrees Celsius.

[0221] The aerosol-generating article 100 further comprises a ring element 115 which overlies the sealing region. The ring element 115 is formed from paper having a grammage of 100 gsm. The ring element 115 has a higher stiffness than the first wall 111 and the second wall 112. The ring element 115 overlies the entire sealing region. The ring element 115 is adhered to the first wall 111. In this way, a portion of the first wall 111 is sandwiched between the ring element 115 and the second wall 112. The ring element 115 is adhered to the first wall 111 by a polyvinyl alcohol adhesive. The ring element 115 has a thickness of 3.5 millimetres, corresponding to the thickness of the contact region 116.

[0222] The spherical beads 114 provided in the substrate compartment 113 have a mean diameter of 1.5 millimetres and a density of 1.3 grams per cubic centimetre. The total weight of beads 114 in the substrate compartment 113 is approximately 150 mg. The beads 114 are formed of an aerosol-generating substrate comprising plant particles, aerosol former and a hydrocolloid binder. An example of a suitable composition of the aerosol-generating substrate forming the beads is provided below.

[0223] Example

[0224] Suitable compositions for forming beads or granules of aerosol-generating substrate according to the invention are set out in Table 1 below:

[0225] Table 1

[0226] All amounts are shown as percentages by weight, on a dry weight basis, based on the total weight of the aerosol-generating element.

[0227] In order to make the beads, the tobacco particles are first mixed with glycerin. The HPMC or CMC binder is dispersed in glycerin and then water is added to form an aqueous binder solution. The binder solution is added to the mixture of tobacco particles and glycerin and all of the components are mixed to form a dough. The dough is extruded to form a plurality of discrete elements and the discrete elements are then spheronized at low speed to form spherical beads having an average diameter of 1.5 millimetres. The beads are dried in an oven to a desired moisture content. The dried beads can then be incorporated into a variety of different aerosol-generating articles, as described above.

[0228] When incorporated into an aerosol-generating article as described above in relation to Figure 1 and heated to a temperature of between 200 and 240 degrees Celsius, an aerosol was generated containing nicotine and glycerin from the aerosol-generating substrate. The ratio of nicotine to glycerin in each puff of aerosol was found to remain consistent over the duration of the heating. This is in contrast to the aerosol generated from an article having a similar construction but in which the aerosol-generating substrate is in the form of tobacco cast leaf. With the tobacco cast leaf substrate, the aerosol generated under the same conditions was found to have a much more variable ratio of nicotine to glycerin per puff. The provision of an aerosol with a more consistent ratio of nicotine to glycerin across puffs provides an optimal sensory experience to the consumer over the duration of the heating.

[0229] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". In this context, therefore, a number A is understood as A ± 10 percent of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

CLAIMS1. An aerosol-generating substrate for use in an aerosol-generating article or system, the aerosol-generating substrate comprising: at least 50 percent by weight of plant particles, on a dry weight basis; at least 10 percent by weight of aerosol former, on a dry weight basis; and one or more hydrocolloid binders, wherein the total amount of hydrocolloid binder is less than or equal to 5 percent by weight of the aerosol-generating substrate, on a dry weight basis, wherein the weight ratio of plant particles to aerosol former in the aerosol-generating substrate is at least 2.5 and wherein the aerosol-generating substrate is in the form of a plurality of beads or granules.

2. An aerosol-generating substrate according to claim 1, wherein the plant particles comprise tobacco particles.

3. An aerosol-generating substrate according to claim 1 or 2, wherein the plant particles have an average particle size of at least 30 microns.

4. An aerosol-generating substrate according to any preceding claim, wherein the weight ratio of plant particles to hydrocolloid binder is at least 20.

5. An aerosol-generating substrate according to any preceding claim, wherein the total amount of hydrocolloid binder is at least 0.5 percent by weight, on a dry weight basis.

6. An aerosol-generating substrate according to any preceding claim, wherein the hydrocolloid binder comprises a cellulosic binder.

7. An aerosol-generating substrate according to claim 6, wherein the cellulosic binder comprises hydroxypropyl methyl cellulose (HPMC).

8. An aerosol-generating substrate according to any preceding claim, wherein the aerosol-generating substrate has a density of at least 0.75 grams per cubic centimetre.

9. An aerosol-generating substrate according to any preceding claim, wherein the bulk density of the plurality of beads or granules is at least 200 mg per cubic centimetre.

10. An aerosol-generating substrate according to any preceding claim, wherein the total surface area of the plurality of beads or granules is at least 120 millimetres squared.

11. An aerosol-generating substrate according to any preceding claim, wherein the mean diameter of the plurality of beads or granules is at least 0.5 millimetre.

12. An aerosol-generating substrate according to any preceding claim, wherein the aerosol-generating substrate is in the form of a plurality of spherical beads.

13. An aerosol-generating article comprising an aerosol-generating substrate according to any preceding claim.

14. An aerosol-generating article according to claim 13, wherein the aerosol-generating article is substantially flat.

15. A method of producing an aerosol-generating substrate according to any of claims 1 to 12, the method comprising the steps of: forming a mixture of plant particles and aerosol former; mixing the combined plant particles and aerosol former with a binder solution comprising one or more hydrocolloid binders to form a dough; forming a plurality of beads or granules from the dough.

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