Modified aerosol-generating element for use in an aerosol-generating article or system

Abstract

There is provided an aerosol-generating element for use in an aerosol-generating article or system. The aerosol-generating element comprises a solid continuous matrix structure and an aerosol-generating formulation dispersed within the solid continuous matrix structure. The aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element. The solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. The aerosol-generating formulation dispersed within the solid continuous matrix structure comprises at least one alkaloid or cannabinoid compound and a polyhydric alcohol. Further, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least 80 percent by weight of a total weight of the aerosol-generating element.

Description

MODIFIED AEROSOL-GENERATING ELEMENT FOR USE IN AN AEROSOLGENERATING ARTICLE OR SYSTEMThe present invention relates to an aerosol-generating element which finds particular use in an aerosol-generating article or system. The present invention further relates to an aerosol-generating article or system comprising such an aerosol-generating element.Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than combusted, are known in the art. Typically in such articles an aerosol is generated by the transfer of heat from a heat source to a physically separate 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 air drawn through the aerosol-generating article. As the released compounds cool, they condense to form an aerosol.A number of prior art documents disclose aerosol-generating devices for consuming aerosol-generating articles. Such devices include, for example, electrically heated aerosol generating devices in which an aerosol is generated by the transfer of heat from one or more electrical heater elements of the aerosol-generating device to the aerosol-generating substrate of a heated aerosol-generating article.Substrates for heated aerosol-generating articles have, in the past, often been produced using randomly oriented shreds, strands, or strips of tobacco material. As an alternative, rods for heated aerosol-generating articles formed from gathered sheets of tobacco material have been disclosed, by way of example, in international patent application WO 2012 / 164009.International patent application WO 2011 / 101164 discloses alternative rods for heated aerosol-generating articles formed from strands of homogenised tobacco material, which may be formed by casting, rolling, calendering or extruding a mixture comprising particulate tobacco and at least one aerosol former to form a sheet of homogenised tobacco material. In alternative embodiments, the rods of WO 2011 / 101164 may be formed from strands of homogenised tobacco material obtained by extruding a mixture comprising particulate tobacco and at least one aerosol former to form continuous lengths of homogenised tobacco material.Substrates for heated aerosol-generating articles typically further comprise an aerosol former, that is, a compound or mixture of compounds that, in use, facilitates formation of the aerosol and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-formers include, but are not limited to: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerin; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.Alternative forms of substrates comprising nicotine have also been disclosed. By way of example, liquid nicotine compositions, often referred to as e-liquids, have been proposed. These liquid compositions may, for example, be heated by a coiled electrically resistive filament of an aerosol-generating device.Substrates of this type may require particular care in the manufacture of the containers holding the liquid composition in order to prevent undesirable leakages.It has been previously proposed to provide an encapsulated nicotine formulation for use as an aerosol-generating substrate. However, the encapsulation of nicotine formulations has been found to be challenging. One of the reasons for this is the preference for hydrophilic aerosol formers, such as glycerin and propylene glycol, in the nicotine formulation, which makes it difficult to use many of the commonly used encapsulation materials, which are also hydrophilic. With existing encapsulation techniques, it has generally been found that such a high level of the hydrophilic encapsulation material is required in order to produce a stable product that an insufficient payload of the nicotine formulation is provided.Whilst hydrophobic encapsulation materials are available, such materials often need to be processed at relatively high temperature, which risks the degradation of the nicotine formulation during manufacture. During use, the temperatures required to generate an aerosol from the nicotine formulation may be sufficiently high to cause degradation of the hydrophobic encapsulation material. This may result in the release of undesirable compounds into the resultant aerosol, which may have an adverse impact on the sensory profile of the aerosol.It has also been proposed to provide a gel composition comprising nicotine that is adapted to generate a nicotine-containing aerosol upon heating. By way of example, WO 2018 / 019543 discloses a thermoreversible gel composition, that is, a gel that becomes fluid when heated to a melting temperature and sets into a gel again at a gelation temperature. WO 2018 / 019543 discloses the provision of such a gel within a housing of a cartridge. The cartridge can be disposed of and replaced when the gel has been consumed. In order for the gel composition to generate a satisfactory amount of aerosol during use, it is desirable for the gel composition to include a significant amount of an aerosol-former, such as glycerol. However, due to the plasticising qualities of glycerol, it has been difficult to provide a gel composition that is capable of providing a good aerosol delivery during use and, at the same time, geometrically stable, that is, a gel composition that does not undergo a significant volume loss as it solidifies and settles into film form.Thus, it would be desirable to provide an alternative, novel encapsulated aerosol generating formulation, such as for example an aerosol-generating element encapsulating anicotine-containing formulation, which provides an improved encapsulated substrate having increased stability and minimal leakage of the aerosol-generating formulation.It would also be desirable to provide such an aerosol-generating element that is easy to handle such as to facilitate the manufacturing and packaging of aerosol-generating articles comprising one or more of the aerosol-generating element. It would also be desirable to provide such an encapsulated aerosol-generating formulation with minimal encapsulating structure, so as to provide an efficient aerosol delivery, particularly when heated to a temperature in the range from about 150 degrees Celsius to about 350 degrees Celsius.The present disclosure relates to an aerosol-generating element for use in an aerosol generating article or system. The aerosol-generating element may comprise a solid continuous matrix structure and an aerosol-generating formulation dispersed within the solid continuous matrix structure. The aerosol-generating formulation may be trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element. The solid continuous matrix structure may be a polymer matrix comprising one or more matrix-forming polymers. The aerosol-generating formulation dispersed within the solid continuous matrix structure may comprise at least one alkaloid or cannabinoid compound. The aerosol-generating formulation dispersed within the solid continuous matrix structure may comprise a polyhydric alcohol. The aerosol-generating formulation dispersed within the solid continuous matrix structure may account for at least about 80 percent by weight of a total weight of the aerosol-generating element.Further, the present disclosure relates to an aerosol-generating article comprising one or more aerosol-generating elements as described above. In addition, the present disclosure relates to an aerosol-generating system comprising one or more aerosol-generating elements or an aerosol-generating article as described above and an electrically operated aerosol generating device comprising a heating element and a heating chamber configured to receive the aerosol-generating element or article so that the aerosol-generating element is heated in the heating chamber by the heating element.According to the present invention there is provided an aerosol-generating element for use in an aerosol-generating article or system, the aerosol-generating element comprising: a solid continuous matrix structure; and an aerosol-generating formulation dispersed within the solid continuous matrix structure, wherein the aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element; wherein the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers, and wherein the aerosol generating formulation dispersed within the solid continuous matrix structure comprises at least one alkaloid or cannabinoid compound and a polyhydric alcohol, wherein the aerosol- generating formulation dispersed within the solid continuous matrix structure accounts for at least about 80 percent by weight of a total weight of the aerosol-generating element.The term “aerosol-generating article” is used herein with reference to the invention to describe an article wherein an aerosol-generating substrate is heated to produce and deliver an aerosol to a consumer. As used herein, the term “aerosol-generating substrate” denotes a substrate capable of releasing volatile compounds upon heating to generate an aerosol.The term “aerosol-generating element” is used herein with reference to the invention to describe a discrete, self-standing aerosol-generating substrate element capable of releasing volatile compounds upon heating to generate an aerosol. An aerosol-generating element in accordance with the present invention may find use as an aerosol-generating substrate of an aerosol-generating article.The aerosol generated from the aerosol-generating formulation of aerosol-generating elements described herein is a dispersion of solid particles or liquid droplets (or a combination of solid particles and liquid droplets) in a gas. The aerosol may be visible or invisible and may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles or liquid droplets or a combination of solid particles and liquid droplets.A conventional cigarette is lit when a user applies a source of ignition to one end of the cigarette and draws air through the other end. The localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke. By contrast, in heated aerosol generating articles, an aerosol is generated by heating a flavour generating substrate, such as, for example, a tobacco-based substrate or a substrate containing an aerosol-former and a flavouring. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol forming material.For example, aerosol-generating articles according to the invention may find particular application in aerosol-generating systems comprising an electrically heated aerosol generating device having an internal heater which is adapted to supply heat to one or more discrete aerosol-generating substrate elements. As used herein with reference to the present invention, the term “aerosol-generating device” is used to described a device comprising a heater element that interacts with one or more aerosol-generating elements in accordance with the invention to produce an aerosol. During use, volatile compounds are released from the aerosol-generating element or elements by heat transfer and entrained in air drawn through the aerosol-generating article. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.Substrates for heated aerosol-generating articles typically comprise an “aerosol former”, that is, a compound or mixture of compounds that, in use, facilitates formation of the aerosol, and that preferably is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Examples of suitable aerosol-formers include: polyhydric alcohols, such as propylene glycol, triethylene glycol, 1,3-butanediol and glycerin; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The polyhydric alcohol in the aerosol-generating article of the invention is also an aerosol former within the meaning set out above.As used herein with reference to the present invention, the term “aerosol-generating formulation” refers to a formulation comprising a plurality of aerosol-generating formulation components, which upon heating of the aerosol-generating element will volatilise to produce an aerosol.As used herein with reference to the present invention, the term “matrix-forming polymer” refers to an encapsulation material in the form of a polymer which is capable of producing a three-dimensional polymer matrix as a result of cross-linking when the matrix forming polymer is brought into contact with a cross-linking solution of multivalent cations. The resultant polymer matrix is capable of trapping and retaining the aerosol-generating formulation within its cross-linked structure. The nature of the cross-linked polymer matrix will be discussed in more detail below.As briefly described above, in contrast with existing aerosol-generating elements, an aerosol-generating element in accordance with the present invention comprises a solid continuous matrix structure and an aerosol-generating formulation dispersed within the solid continuous matrix structure. In more detail, the aerosol-generating formulation is trapped within the solid continuous matrix structure and can be released from the solid continuous matrix structure upon heating of the aerosol-generating element to a predetermined temperature.Without wishing to be bound by theory, it is understood that in an aerosol-generating element in accordance with the present invention a three-dimensional polymeric matrix structure is formed by cross-linking, and aerosol-generating formulation is retained within the polymeric matrix structure. This is, in particular, in contrast with existing core / shell structures wherein a content of the core is released upon rupturing the shell.In an aerosol-generating element in accordance with the present invention the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. Further, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 80 percent by weight of a total weight of the aerosol-generating element.Advantageously, the invention provides an aerosol-generating formulation in encapsulated form that has a significantly lower content of encapsulation material (corresponding to the one or more matrix-forming polymers of the solid continuous matrix structure) compared with previously available substrates. As such, the levels of the aerosol generating formulation components, such as the alkaloid or cannabinoid and the polyhydric alcohol, can advantageously be maximised within the aerosol-generating element. Further, the reduction in the proportion of encapsulation material required enables a more efficient generation of aerosol upon heating, since less of the heat supplied to the aerosol-generating element is used for increasing the temperature of the encapsulation material.The polymer-based solid continuous matrix of aerosol-generating articles in accordance with the present invention provides an inert encapsulation structure for retaining and immobilising the aerosol-generating formulation, which is stable upon heating of the aerosol generating element during use. The inventors have found that, when heated to temperatures in the range from 150 degrees Celsius to 350 degrees Celsius, aerosol-generating elements in accordance with the present invention release an aerosol as they undergo a significant weight loss. This weight loss is not, however, accompanied by an equally significant volume loss. Without wishing to be bound by theory, it is understood that, upon heating, components of the aerosol-generating formulation originally dispersed and trapped within the solid continuous matrix structure are substantially vaporised and released. On the other hand, components of the solid continuous matrix are substantially unaffected and the solid continuous matrix only partially shrinks while essentially retaining its 3D structure. As such, the encapsulation of the aerosol-generating formulation within the polymer-based matrix advantageously provides minimal or no adverse effects on the sensory profile of the aerosol generated upon heating.The aerosol-generating element of the present invention has been found to advantageously provide a controlled delivery of aerosol. Furthermore, the aerosol delivery profile can be readily adjusted by adjusting parameters of the aerosol-generating element such as the size, shape, structure and formulation of the aerosol-generating element.The invention advantageously provides an aerosol-generating element that is in the form of a discrete, self-standing solid object which is sufficiently stable and robust that it can readily be processed and introduced into an aerosol-generating article using existing methods and techniques.Further, aerosol-generating elements in accordance with the present invention can be prepared by a cost-effective method that can be carried out with existing equipment, as will become apparent from the following description thereof. In addition, aerosol-generating elements in accordance with the present invention can be prepared by a method that can beeasily incorporated into existing production lines for the manufacture of aerosol-generating articles.Aerosol-generating elements in accordance with the present invention may be prepared from a matrix precursor solution and components of an aerosol-generating formulation. By way of example, in a method of manufacturing an aerosol-generating element in accordance with the invention, a matrix precursor solution may be provided that comprises a matrix forming polymer in water. Preferably, the matrix polymer solution comprises at least about 35 percent by weight of water, more preferably at least about 40 percent by weight of water. This level of water ensures that the matrix-forming polymer is sufficiently dissolved so that a homogeneous solution is provided.The matrix-forming polymer may be a single polymer or a combination of two or more polymers, wherein the one or more polymers are capable of forming a cross-linked matrix through an ionotropic gelation mechanism in a cross-linking solution of multivalent cations. The cross-linking of the matrix-forming polymer is achieved through reaction of the polymer with multivalent cations in the cross-linking solution, which form salt bridges to cross-link the polymer molecules. Suitable matrix-forming polymers would be known to the skilled person, and include, but are not limited to, alginate, pectin, hydroxyethylmethacryate (HEMA), N-(2-hydroxy propyl)methacrylate (HPMA), N-vinyl-2-pyrrolidone (NVP), N-isopropylacrylamide (NIPAMM), vinyl acetate (VAc), acrylic acid (AA), methacrylic acid (MAA), polyethylene glycol acrylate / methacrylate (PEGA / PEGMA) and polyethylene glycol diacrylate / dimethacrylate, (PEGDA / PEGDMA).Preferably, the matrix-forming polymer comprises one or more polysaccharides, such as alginate or pectin, or a combination thereof. Polysaccharides are particularly suitable for use in the present invention, since they can be made water insoluble and heat stable through cross-linking, and are tasteless. There is therefore no adverse impact on the sensory properties of the aerosol generated from the aerosol-generating element. Alternative matrix forming polymers suitable for use in methods according to the invention include but are not limited to chitosan, fibrin, collagen, gelatin, hyaluronic acid, dextran and combinations thereof.In preferred embodiments, the matrix-forming polymer is a single polysaccharide. Even more preferably the matrix-forming polymer is alginate. In other words, in such particularly preferred embodiments, the solid continuous matrix structure is an alginate polymer matrix. In a first step, a plurality of aerosol-generating formulation components may be added to the matrix precursor solution to form an aerosol-generating solution, wherein the aerosol generating formulation components comprise at least one alkaloid or cannabinoid compound and a polyhydric alcohol. As used herein when describing a method of preparing aerosol generating elements in accordance with the invention, the term “aerosol-generating solution” denotes a solution of the aerosol-generating formulation components and the matrix precursors, in an appropriate solvent.Polyhydric alcohols suitable for use in the aerosol-generating element include, but are not limited to, propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin. Preferably, in an aerosol-generating element produced in accordance with the invention the polyhydric alcohol is selected from the group consisting of glycerin, propylene glycol, and combinations thereof. In particularly preferred embodiments the polyhydric alcohol is glycerin. Preferably, the alkaloid is selected from the group consisting of: nicotine, anatabine and combinations thereof.It may be desirable to control the viscosity of aerosol-generating solution. This may include controlling the viscosity of the matrix polymer solution as the aerosol-generating formulation components are added. For example, depending upon the technique used for producing the discrete portion of the aerosol-generating solution in the subsequent step of the method, it may be preferable to provide the aerosol-generating solution with a viscosity within a specific range. Different techniques are likely to be facilitated by different viscosity solutions and an appropriate viscosity should therefore be determined depending upon the technique used. By way of example, when the discrete portion of the aerosol-generating solution is produced in a gravitational dripping process, the viscosity of the solution is preferably retained below about 5000 mPa.s. (milliPascal-seconds). This enables droplets of the aerosol generating solution to be formed under gravity and also allows the beads to reach a stable shape in the cross-linking solution before the cross-linking hardens the solution and fixes the final shape of the aerosol-generating element.In certain cases, in order to control the viscosity of the aerosol-generating solution it may be preferably to control the pH of the matrix polymer solution whilst the aerosol-generating formulation components are being added. This is because for some matrix polymer solutions, the pH may affect the viscosity. For example, in embodiments of the invention in which the matrix-forming polymer comprises alginate, it is preferable to retain the pH of the solution above pH4. This is intended to avoid any gelling of the alginate, which may occur at pH levels below pH4, for example, due to hydrogen bonding. Such gelling at a low pH would cause an undesirable increase in the viscosity of the aerosol-generating solution, which would make it difficult to use certain techniques such as gravitational dripping, in order to form the aerosol generating element.Alternatively or in addition, the viscosity of the aerosol-generating solution may be controlled by adjusting the concentration of the solution. For example, the proportion of water in the aerosol-generating solution may be adjusted in order to adjust the viscosity. Preferably, the aerosol-generating solution comprises at least about 35 percent by weight of water in order to maintain a suitable viscosity. Particularly preferably, the aerosol-generating solutioncomprises between about 35 percent by weight and about 65 percent by weight of water. In a second step, a discrete portion of the aerosol-generating solution may be formed. In a third step, the formed discrete portion of the aerosol-generating solution may be added to a cross-linking solution of multivalent cations to cross-link the matrix-forming polymer, thereby forming an aerosol-generating element having a continuous polymer matrix structure and an aerosol generating formulation comprising the aerosol-generating components dispersed within the continuous polymer matrix. Preferred multivalent cations include calcium, iron, aluminium, manganese, copper, zinc or lanthanum. A particularly preferred salt is calcium chloride.In certain preferred embodiments of the invention in which the aerosol-generating solution comprises an acid, the calcium salt provided in the cross-linking solution may advantageously be a salt of the same acid. For example, in embodiments in which the aerosol generating solution comprises lactic acid, the cross-linking solution may advantageously comprise calcium lactate.Where the aerosol-generating solution comprises nicotine, the acid in the aerosol generating solution forms a nicotine salt with the nicotine. The use of a calcium salt corresponding to the acid in the aerosol-generating solution therefore provides the same salt in the cross-linking solution as in the aerosol-generating solution. This, in turn, advantageously limits the diffusion of nicotine salts out of the aerosol-generating solution into the cross-linking solution during the cross-linking step. A higher concentration of the nicotine salt can therefore be retained within the aerosol-generating element. Furthermore, any potential waste of the nicotine and acid during the production of the aerosol-generating element can be reduced.Preferably, the cross-linking solution further comprises a polyhydric alcohol, which is the same as the polyhydric alcohol selected as the aerosol-generating formulation component. The inclusion of the polyhydric alcohol in the cross-linking solution has been found to limit diffusion of the polyhydric alcohol from the aerosol-generating solution into the cross-linking solution during the cross-linking step. This advantageously enables a higher concentration of the polyhydric alcohol to be retained within the aerosol-generating element than has been previously possible.In a fourth step, the aerosol-generating element may be removed from the cross-linking solution and dried. As described briefly above, in an aerosol-generating element in accordance with the present invention the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 80 percent by weight of a total weight of the aerosol-generating element.More preferably, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 82 percent by weight of a total weight of the aerosol-generating element. Even more preferably, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 84 percent by weight of a total weight of the aerosol-generating element.In particularly preferred embodiments, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 86 percent by weight of a total weight of the aerosol-generating element. More preferably, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 88 percent by weight of a total weight of the aerosol-generating element. Even more preferably, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 90 percent by weight of a total weight of the aerosol generating element.Most preferably, the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 92 percent by weight of a total weight of the aerosol-generating element or at least about 93 percent by weight of a total weight of the aerosol-generating element or at least about 94 percent by weight of a total weight of the aerosol-generating element or at least about 95 percent by weight of a total weight of the aerosol-generating element.In aerosol-generating elements wherein the aerosol-generating formulation accounts for a fraction of the overall weight of the aerosol-generating element within the ranges described above, it is advantageously possible to minimise the portion of heat supplied to the aerosol generating element during use that is consumed for increasing the temperature of the encapsulation material. As such, a more efficient use of the heat supplied to the aerosol generating element is made possible, such that the great majority of said heat is effectively employed for releasing the aerosol-formulation components from the solid continuous matrix structure and the generation of an aerosol.As set out above, in aerosol-generating elements in accordance with the present invention, the solid continuous matrix structure is a polymer matrix comprising one or more matrix-forming polymers. Suitable matrix-forming polymers would be known to the skilled person.Preferably, the one or more matrix-forming polymer include one or more polysaccharides. More preferably, the one or more matrix-forming polymers include at least one of alginate and pectin. Polysaccharides are particularly suitable for use in the present invention, since they can be made water insoluble and heat stable through cross-linking, and are tasteless. There is therefore no adverse impact on the sensory properties of the aerosol generated from the aerosol-generating element.In preferred embodiments, the matrix-forming polymer is a single polysaccharide. Even more preferably the matrix-forming polymer is alginate. In other words, in such particularly preferred embodiments, the solid continuous matrix structure is an alginate polymer matrix.Use of alginate as the sole matrix-forming polymer is preferred because alginate has the ability to promote the rapid formation of insoluble, solid aerosol-generating elements. In more detail, the inventors have found that use of alginate as the sole matrix-forming polymer, particularly in the amounts described below, advantageously provides aerosol-generating elements that are stable and self-supporting and can hold higher concentrations of polyhydric alcohol within the polymer matrix. Further, compared to other formulations, use of alginate as the sole matrix-forming polymer, particularly in the amounts described below has been found to allow for larger aerosol-generating elements to be formed - for example, in the form of spherical or quasi-spherical beads having larger diameters.Preferably, in an aerosol-generating element in accordance with the present invention, the solid continuous matrix structure is an alginate polymer matrix and the aerosol-generating element comprises at least about 1 percent by weight of alginate. More preferably, the aerosol-generating element comprises at least about 1.5 percent by weight of alginate. Even more preferably, the aerosol-generating element comprises at least about 2 percent by weight of alginate.In particularly preferred embodiments, the aerosol-generating element comprises at least about 3 percent by weight of alginate.Preferably, in an aerosol-generating element in accordance with the present invention, the solid continuous matrix structure is an alginate polymer matrix and the aerosol-generating element comprises less than or equal to about 10 percent by weight of alginate. More preferably, the aerosol-generating element comprises less than or equal to about 8 percent by weight of alginate. Even more preferably, the aerosol-generating element comprises less than or equal to about 6 percent by weight of alginate.In particularly preferred embodiments, the aerosol-generating element comprises less than or equal to about 5 percent by weight of alginate.In some embodiments, the solid continuous matrix structure is an alginate polymer matrix and the aerosol-generating element comprises from about 1 percent by weight to about 10 percent by weight of alginate. Preferably, the aerosol-generating element comprises from about 1.5 percent by weight to about 10 percent by weight of alginate, more preferably from about 2 percent by weight to about 10 percent by weight of alginate, even more preferably from about 3 percent by weight to about 10 percent by weight of alginate.In other embodiments, the solid continuous matrix structure is an alginate polymer matrix and the aerosol-generating element comprises from about 1 percent by weight to about 8 percent by weight of alginate. Preferably, the aerosol-generating element comprises from about 1.5 percent by weight to about 8 percent by weight of alginate, more preferably from about 2 percent by weight to about 18 percent by weight of alginate, even more preferably from about 3 percent by weight to about 8 percent by weight of alginate.In further embodiments, the solid continuous matrix structure is an alginate polymer matrix and the aerosol-generating element comprises from about 1 percent by weight to about 6 percent by weight of alginate. Preferably, the aerosol-generating element comprises from about 1.5 percent by weight to about 6 percent by weight of alginate, more preferably from about 2 percent by weight to about 6 percent by weight of alginate, even more preferably from about 3 percent by weight to about 6 percent by weight of alginate.Alternative matrix-forming polymers suitable for use in aerosol-generating elements in accordance with the invention include, but are not limited to, chitosan, fibrin, collagen, gelatin, hyaluronic acid, dextran and combinations thereof.Further alternative matrix-forming polymers suitable for use in aerosol-generating elements in accordance with the invention may be built from one or more of the following monomers and polymers: hydroxyethylmethacryate (HEMA), N-(2-hydroxy propyl)methacrylate (HPMA), N-vinyl-2-pyrrolidone (NVP), N-isopropylacrylamide (NIPAMM), vinyl acetate (VAc), acrylic acid (AA), methacrylic acid (MAA), polyethylene glycol acrylate / methacrylate (PEGA / PEGMA) and polyethylene glycol diacrylate / dimethacrylate, (PEGDA / PEGDMA).As defined above, an aerosol-generating element in accordance with the invention comprises a polyhydric alcohol as a component of the aerosol-generating formulation dispersed within the solid continuous matrix structure.The polyhydric alcohol acts as the aerosol former of the aerosol-generating element. Polyhydric alcohols suitable for use in the aerosol-generating element include, but are not limited to, propylene glycol, triethylene glycol, 1,3-butanediol, and glycerin. Preferably, in an aerosol-generating element in accordance with the invention the polyhydric alcohol is selected from the group consisting of glycerin, propylene glycol, and combinations thereof. In particularly preferred embodiments the polyhydric alcohol is glycerin.Preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for at least 30 percent by weight based on the total weight of the aerosol-generating element. Thus, one such aerosol-generating element comprises at least about 30 percent by weight of the polyhydric alcohol.In some embodiments, the polyhydric alcohol content in the aerosol-generating formulation preferably accounts for at least about 35 percent by weight based on the total weight of the aerosol-generating element. As such, an aerosol-generating element in accordance with the present invention comprises at least about 35 percent by weight of the polyhydric alcohol. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for at least 40 percent by weight based on the total weight of the aerosol generating element.In particularly preferred embodiments, the polyhydric alcohol content in the aerosol generating formulation accounts for at least about 45 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for at least about 50 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for at least about 55 percent by weight based on the total weight of the aerosol-generating element. Most preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for at least about 60 percent by weight or at least about 65 percent by weight or at least about 70 percent by weight based on the total weight of the aerosol-generating element.Typically, in an aerosol-generating element in accordance with the invention the polyhydric alcohol content in the aerosol-generating formulation accounts for less than or equal to about 95 percent by weight based on the total weight of the aerosol-generating element.Preferably, in an aerosol-generating element in accordance with the invention the polyhydric alcohol content in the aerosol-generating formulation accounts for less than or equal to about 90 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for less than or equal to about 85 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for less than or equal to about 80 percent by weight based on the total weight of the aerosol-generating element.In preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 30 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element. Preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 35 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 40 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 45 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element. In particularly preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 50 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element, more preferably from about 55 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element, even more preferably from about 60 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element. Most preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 65 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element or even from about 70 percent by weight to about 95 percent by weight based on the total weight of the aerosol-generating element.In these embodiments, the aerosol-generating element may comprise from about 30 percent by weight to about 95 percent by weight of polyhydric alcohol. More preferably, the aerosol-generating element comprises from about 35 percent by weight to about 95 percent by weight of polyhydric alcohol. Even more preferably, the aerosol-generating element comprises from about 40 percent by weight to about 95 percent by weight of polyhydric alcohol. Most preferably, the aerosol-generating element comprises from about 45 percent by weight to about 95 percent by weight of polyhydric alcohol. In particularly preferred embodiments, the aerosol-generating element comprises from about 50 percent by weight to about 95 percent by weight of polyhydric alcohol, preferably from about 55 percent by weight to about 95 percent by weight of polyhydric alcohol, more preferably from about 60 percent by weight to about 95 percent by weight of polyhydric alcohol, even more preferably from about 65 percent by weight to about 95 percent by weight of polyhydric alcohol, most preferably from about 70 percent by weight to about 95 percent by weight of polyhydric alcohol.In other embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 30 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element. Preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 35 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 40 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 45 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element. In particularly preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 50 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element, more preferably from about 55 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element, even more preferably from about 60 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element. In most preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 65 percent by weight to about 90 percent by weight or even from about 70 percent by weight to about 90 percent by weight based on the total weight of the aerosol-generating element.In these embodiments, the aerosol-generating element in accordance with the present invention may comprise from about 30 percent by weight to about 90 percent by weight of a polyhydric alcohol. Preferably, the aerosol-generating element comprises from about 35 percent by weight to about 90 percent by weight of polyhydric alcohol. More preferably, the aerosol-generating element comprises from about 40 percent by weight to about 90 percent by weight of polyhydric alcohol. Even more preferably, the aerosol-generating element comprises from about 45 percent by weight to about 90 percent by weight of polyhydric alcohol. In particularly preferred embodiments, the aerosol-generating element comprises from about 50 percent by weight to about 90 percent by weight of polyhydric alcohol, preferably from about 55 percent by weight to about 90 percent by weight of polyhydric alcohol, more preferably from about 60 percent by weight to about 90 percent by weight of polyhydric alcohol, even more preferably from about 65 percent by weight to about 90 percent by weight of polyhydric alcohol, most preferably from about 70 percent by weight to about 90 percent by weight of polyhydric alcohol.In further embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 30 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element. Preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 35 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 40 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 45 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element. In particularly preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 50 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element, more preferably from about 55 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element, even more preferably from about 60 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element. In most preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 65 percent by weight to about 85 percent by weight or even from about 70 percent by weight to about 85 percent by weight based on the total weight of the aerosol-generating element.In these embodiments, the aerosol-generating element in accordance with the present invention may comprise from about 30 percent by weight to about 85 percent by weight of a polyhydric alcohol. Preferably, the aerosol-generating element comprises from about 35 percent by weight to about 85 percent by weight of polyhydric alcohol. More preferably, the aerosol-generating element comprises from about 40 percent by weight to about 85 percent by weight of polyhydric alcohol. Even more preferably, the aerosol-generating element comprises from about 45 percent by weight to about 85 percent by weight of polyhydric alcohol. In particularly preferred embodiments, the aerosol-generating element comprises from about 50 percent by weight to about 85 percent by weight of polyhydric alcohol, preferably from about 55 percent by weight to about 85 percent by weight of polyhydric alcohol, more preferably from about 60 percent by weight to about 85 percent by weight of polyhydric alcohol, even more preferably from about 65 percent by weight to about 85 percent by weight of polyhydric alcohol, most preferably from about 70 percent by weight to about 85 percent by weight of polyhydric alcohol.In yet further embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 30 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element. Preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 35 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element. More preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 40 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element. Even more preferably, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 45 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element. In particularly preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 50 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element, more preferably from about 55 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element, even more preferably from about 60 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element. In most preferred embodiments, the polyhydric alcohol content in the aerosol-generating formulation accounts for from about 65 percent by weight to about 80 percent by weight or even from about 70 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element.In such embodiments, the aerosol-generating element in accordance with the present invention may comprise from about 30 percent by weight to about 80 percent by weight of a polyhydric alcohol. Preferably, the aerosol-generating element comprises from about 35 percent by weight to about 80 percent by weight of polyhydric alcohol. More preferably, the aerosol-generating element comprises from about 40 percent by weight to about 80 percent by weight of polyhydric alcohol. Even more preferably, the aerosol-generating element comprises from about 45 percent by weight to about 80 percent by weight of polyhydric alcohol. In particularly preferred embodiments, the polyhydric alcohol content in the aerosol- generating formulation accounts for from about 50 percent by weight to about 80 percent by weight, preferably from about 55 percent by weight to about 80 percent by weight, more preferably from about 60 percent by weight to about 80 percent by weight, even more preferably from about 65 percent by weight to about 80 percent by weight, most preferably from about 70 percent by weight to about 80 percent by weight based on the total weight of the aerosol-generating element.As described briefly above, in an aerosol-generating element in accordance with the present invention the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises at least one alkaloid or cannabinoid compound. In some embodiments, the aerosol-generating formulation dispersed within the solid continuous matrix structure comprises both an alkaloid compound and a cannabinoid compound.As used herein with reference to the invention, the term “alkaloid compound” is used to describe any one of a class of naturally occurring organic compounds that contain one or more basic nitrogen atoms. Generally, an alkaloid contains at least one nitrogen atom in an amine-type structure. This or another nitrogen atom in the molecule of the alkaloid compound can be active as a base in acid-base reactions. Most alkaloid compounds have one or more of their nitrogen atoms as part of a cyclic system, such as for example a heterocylic ring. In nature, alkaloid compounds are found primarily in plants, and are especially common in certain families of flowering plants. However, some alkaloid compounds are found in animal species and fungi. In the context of the present invention, the term “alkaloid compounds” is used to describe both naturally derived alkaloid compounds and synthetically manufactured alkaloid compounds. Suitable alkaloid compounds for use in an aerosol-generating element in accordance with the invention include, but are not limited to, nicotine and anatabine.As used herein with reference to the invention, the term “cannabinoid compound” is used to describe any one of a class of naturally occurring compounds that are found in parts of the cannabis plant - namely the species Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Cannabinoid compounds are especially concentrated in the female flower heads. Cannabinoid compounds naturally occurring the in cannabis plant include tetrahydrocannabinol (THC) and cannabidiol (CBD). In the context of the present invention, the term “cannabinoid compounds” is used to describe both naturally derived cannabinoid compounds and synthetically manufactured cannabinoid compounds.Cannabinoid compounds suitable for use in an aerosol-generating film in accordance with the invention include 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).In general, the aerosol-generating element may comprise up to about 10 percent by weight of an alkaloid compound or a cannabinoid compound or both. In view of applications of the aerosol-generating element of the invention as a substrate in an aerosol-generating article, this is advantageous as the content of alkaloid compound or cannabinoid compound or both in the element may be increased and adjusted with a view to optimising the delivery of alkaloid compound or cannabinoid compound or both in aerosol form to a consumer. Compared with existing aerosol-generating substrates based on the use of plant material, this may advantageously allow for higher contents of alkaloid compound or cannabinoid compound or both per volume of substrate (element or elements) or per weight of substrate (element or elements), which may be desirable from a manufacturing viewpoint.

Claims

CLAIMS1. An aerosol-generating element for use in an aerosol-generating article or system, the aerosol-generating element comprising:a solid continuous matrix structure; andan aerosol-generating formulation dispersed within the solid continuous matrix structure, wherein the aerosol-generating formulation is trapped within the solid continuous matrix structure and releasable from the solid continuous matrix structure upon heating of the aerosol-generating element;wherein the solid continuous matrix structure is an alginate matrix, and wherein the aerosol generating formulation dispersed within the solid continuous matrix structure comprises at least one alkaloid or cannabinoid compound, a polyhydric alcohol, and a carboxylic acid; wherein the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 80 percent by weight of a total weight of the aerosol generating element; and wherein the aerosol-generating element comprises less than about 15 percent by weight of water.

2. An aerosol-generating element according to any one of the preceding claims, wherein the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 90 percent by weight of a total weight of the aerosol-generating element.

3. An aerosol-generating element according to claim 1 or 2, wherein the polyhydric alcohol is glycerin, propylene glycol, or a combination of glycerin and propylene glycol.

4. An aerosol-generating element according to any one of the preceding claims, wherein the polyhydric alcohol content in the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least 30 percent by weight of a total weight of the aerosol-generating element.

5. An aerosol-generating element according to any one of the preceding claims, wherein the content of the at least one alkaloid or cannabinoid compound in the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least 0.5 percent by weight of a total weight of the aerosol-generating element.

6. An aerosol-generating element according to any one of the preceding claims, wherein the at least one alkaloid or cannabinoid compound is selected from nicotine, anatabine, cannabidiol (CBD) and tetrahydrocannabinol (THC).

7. An aerosol-generating element according to any one of the preceding claims, wherein the carboxylic acid is lactic acid or levulinic acid.

8. An aerosol-generating element according to any one of the preceding claims, wherein the carboxylic acid content in the aerosol-generating formulation dispersed within the solid continuous matrix structure accounts for at least about 0.5 percent by weight of a total weight of the aerosol-generating element.

9. An aerosol-generating element according to any one of the preceding claims further comprising less than about 10 percent by weight of water.

10. An aerosol-generating element according to any one of the preceding claims having an equivalent diameter of at least about 0.5 millimetres.

11. An aerosol-generating element according to any one of the preceding claims having an equivalent diameter of less than or equal to about 6 millimetres.

12. An aerosol-generating element according to any one of the preceding claims having an ovality from about 2 percent to about 30 percent.

13. An aerosol-generating element according to any one of the preceding claims having an exposed surface area to volume ratio from about 0.083 cm-1 to about 24 cm-1.