Method for producing a substrate for an aerosol generating article and associated substrate

Abstract

The present invention concerns a method for producing a substrate for an aerosol generating article adapted to operate with a heat-not-burn aerosol generating device, the method comprising: - forming (110) a gel portion: by forming (112) a pre-mixture of an aerosol forming agent and a thickening agent; by heating (114) the pre-mixture; by adding (116) water to the pre-mixture; - adding (120) to the gel portion an active substrate portion to form a substrate dough.

Description

[0001] Method for producing a substrate for an aerosol generating article and associated substrate

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a method for producing a substrate for an aerosol generating article. The present invention also concerns a substrate produced by such a method and an aerosol generating article comprising such a substrate.

[0004] Particularly, the aerosol generating article is designed to operate with an aerosol generating device and the substrate comprised in the aerosol generating article is able to form aerosol when being heated by the aerosol generating device. Thus, such type of aerosol generating devices, also known as heat-not-burn devices, is adapted to heat, rather than burn to generate aerosol for inhalation.

[0005] BACKGROUND OF THE INVENTION

[0006] The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit smoking traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm vaporizable substances as opposed to burning tobacco in conventional tobacco products.

[0007] A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn device. Devices of this type generate aerosol or vapour by heating an aerosol generating substrate that is usually comprised in a separate consumable article. Typically, such aerosol generating substrate comprises moist leaf tobacco or other suitable vaporizable material to a temperature typically in the range 150°C to 350°C. Heating an aerosol generating substrate, but not combusting or burning it, releases aerosol that comprises the components sought by the user but not products of combustion and burning. Furthermore, the aerosol produced by heating the tobacco or other vaporizable materials does not typically comprise the burnt or bitter taste resulting from combustion and burning that can be unpleasant for the user and the smoke that can be irritating and polluting for the surroundings. Aerosol generating articles, usable with such type of aerosol generating devices can take various forms. Some of them can present an elongated stick or any other suitable shape, like for example a flat shape. Generally, such an aerosol generating article is received at least partially in a heating chamber of the device which comprises one or several heaters to heat the article.

[0008] The substrate comprised in an aerosol generating article comprises generally aerosol formers able to form aerosol when the substrate is being heated. The quantity of aerosol formed by the substrate depends thus on the content of the aerosol formers in the substrate. It is usually desirable to increase this content to increase the quantity of aerosol formed by the substrate. However, known methods for producing the substrate do not allow increasing significantly this content. For example, in substrates produced by some known methods, the aerosol former content ranges from 10 wt.% to 25 wt.%. This might be not sufficient to form the desired quantity of aerosol when the substrate is being heated.

[0009] SUMMARY OF THE INVENTION

[0010] One of the aims of the invention is to propose a method for producing a substrate for an aerosol generating article allowing increasing significantly the content of the aerosol formers in the substrate and as a consequence, the quantity of the aerosol generated by the substrate when it is being heated.

[0011] For this purpose, the invention relates to a method for producing a substrate for an aerosol generating article adapted to operate with a heat-not-burn aerosol generating device, the method comprising:

[0012] - forming a gel portion: by forming a pre-mixture of an aerosol forming agent and a thickening agent; by heating the pre-mixture; by adding water to the pre-mixture;

[0013] - adding to the gel portion an active substrate portion to form a substrate dough.

[0014] The method can also include a step of forming the substrate from the substrate dough. According to the invention, the substrate dough is obtained by mixing a wet material portion (i.e. gel portion) with a dry material portion (i.e. active substrate portion). The gel portion produced according to the invention contains an increased quantity of the aerosol forming agent (in comparison with gels obtained according to prior art methods) while ensuring good binding properties and high viscosity level. Addition of the aerosol forming agent in the gel reduces the water portion in the gel and provides good binding properties and sufficient viscosity for substrate dough formation. Thus, even a small quantity of water is sufficient to ensure these properties. This allows increasing up to 90 wt.% of the aerosol forming agent in the gel. Consequently, the content of the aerosol forming agent in the resulting substrate can be increased for example up to 60 wt.% in dry basis. This leads to a faster aerosol generation by the article and a greater quantity of the aerosol released during a vaping phase.

[0015] According to some embodiments, the pre-mixture is heated before adding the water to the pre-mixture. Heating the pre-mixture before adding water ensures a fast, reliable, reproducible and controllable gel formation.

[0016] According to some embodiments, the gel is formed by mixing:

[0017] - between 80 wt.% and 96 wt.%, preferably 90 wt.%, of the aerosol forming agent;

[0018] - between 1 wt.% and 10 wt.%, preferably 5 wt.%, of the thickening agent;

[0019] - between 1 wt.% and 10 wt.%, preferably 5 wt.%, of water.

[0020] It is thus possible to increase the content of the aerosol forming agent in the gel up to 90 wt.% while ensuring good binding properties and high viscosity level of the gel.

[0021] According to some embodiments, the thickening agent may be selected from the group consisting of agar, gellan gum, tamarid gum, modified starch, hydroxypropyl cellulose, carboxymethylcellulose (CMC) or a combination thereof.

[0022] According to some embodiments, the thickening agent comprises a mixture of agar and carboxymethylcellulose mixed in a ratio comprised between 10:90 and 90:10, preferably between 40:60 and 60:40, most preferably about 50:50.

[0023] This special combination of the components of the thickening agent is beneficial for achieving desired gel viscosity and binding properties in presence of high aerosol former content. Additionally, the stickiness of the resulting substrate dough can be reduced as well as the stickiness of the resulting laminated sheet when a laminating process of the substrate dough is used.

[0024] Additionally or alternatively, the thickening agent may comprise hydroxypropyl cellulose and guar gum, preferably in combination with agar and / or CMC.

[0025] According to some embodiments, the pre-mixture of the aerosol forming agent and the thickening agent forms a suspension.

[0026] In other words, the thickening agent is suspended in the aerosol forming agent. Heating and water addition lead to an even mixture of the thickening and aerosol forming agents. This allows forming a gel.

[0027] Preferably, water is added after the suspension of aerosol forming agent as a liquid and thickening agent is formed. More preferably, the pre-mixture is heated before water is added. Since, no water is added in the pre-mixture, the gel is not formed yet and the thickening agent remains suspended in the aerosol forming agent.

[0028] Additionally, when the thickening agent comprises agar, heating is generally necessary to jellify the agar. If the pre-mixture (containing notably glycerin, CMC and agar) is heated up before water is added, jellification of agar happens quicker compared to the case when water is added to the cold pre-mixture and the pre-mixture is heated afterwards. Using a thickening agent that comprises CMC and agar further allows to obtain a gel with high viscosity while maintaining the water content very low. In contrast, adding water to such pre-mixture before the pre-mixture is heated can lead to inhomogeneous gel formation, where not enough free water is available to be absorbed by the agar, since the CMC would bind a considerable part of the water already at room temperature.

[0029] Alternatively, in some embodiments, water is first added to the pre-mixture and the pre-mixture is then heated.

[0030] According to some embodiments, the pre-mixture is heated to a temperature of at least 60°C, preferably between 65°C and 80°C. According to some embodiments, the method further comprises forming a substrate from the substrate dough. The substrate can present a solid body or bodies, preferably a sheet, strips, threads, or beads.

[0031] The substrate can be formed using for example an embossing / debossing process or a stamping process or a molding process. A combination of these processes can also be used. Alternatively or additionally, a more complex forming process, such for example extrusion of slabs or chunks and lamination into a sheet or strips, can be used. The lamination may enable to form thin sheets of about 0,1 to 1 ,2 mm to facilitate aerosolization and reduce heating energy consumption.

[0032] According to some embodiments, the substrate can further be cut / formed to fit the dimensions of a substrate part of the aerosol generating article. The substrate can be cut / formed, e.g., to a length of 5-20 mm and a width of 2-10 mm.

[0033] Additionally, during the step of forming the substrate from the substrate dough, aerosol channels can be formed on a surface of the substrate or through the substrate. These channels allow conducting airflow and releasing aerosol to be delivered to the user.

[0034] Moreover, a relatively low content of water in the resulting substrate facilitates the forming of the substrate in parts or sheet and can ensure the desired moisture content in the substrate so as no additional drying step can be necessary. This allows simplifying the manufacturing process of the aerosol generating article and reducing energy consumption. This can be particularly convenient for substrates having a particular shape, for example a flat shape.

[0035] According to some embodiments, drying is at least partially performed after forming the substrate to achieve the desired moisture content in the substrate. The desired moisture content in the substrate is chosen based on the shape of the substrate, its heating method, power of the aerosol generating device, composition of the substrate, etc.

[0036] For example, in some embodiments, the substrate having a water content between 9 wt.% and 12 wt.% before drying can be dried to reduce its water content between 6 wt.% to 9 wt.%. According to some embodiments, the substrate is laminated into a sheet. The thickness of the sheet can be lower than 1200 pm, advantageously lower than 400 pm.

[0037] The lamination can for example be performed before drying. The substrate in a form of a sheet can for example be used in a flat-shaped aerosol generating article. According to some examples, the sheet can be folded or rolled to form several layers.

[0038] According to some embodiments, the substrate contains between 30 wt.% and 50 wt.% of the aerosol forming agent in dry basis.

[0039] This content of the aerosol forming agent in the resulting substrate is particularly advantageous to achieve a faster aerosol generation by the article and a greater quantity of the aerosol released during a vaping phase.

[0040] According to some embodiments, the active substrate portion comprises or is formed by at least one plant material and / or fiber material and / or nicotine. In some embodiments, the at least one plant material comprises leaf tobacco particles and / or non-tobacco botanical or extract of non-tobacco botanical. The fiber material can comprise cellulose fibers and / or citrus fibers.

[0041] In some embodiments, the at least one plant material is mixed with the fiber material in a ratio comprised between 3:1 to 6:1.

[0042] Alternatively, the at least one plant material can be provided with a lower proportion of the fiber material. In some examples, no fiber material is provided. In this case, the substrate can have a higher moisture content.

[0043] In some embodiments, the tobacco particle size D90 is comprised between 120 pm and 5 mm, preferably between 500 pm and 900 pm.

[0044] By “particle size D90”, it is understood that 90% of all particles have the size comprised in a specified range or greater than a specified value or lower than a specified value. The particle size is measured by Mastersizer-3000 Aero dry S.

[0045] This particle size has a particular advantage in the resulting substrate. Particularly, since the surface to volume ratio of the individual particles decreases with higher particle size, less water-soluble compounds from tobacco migrate into the gel portion of the substrate. This is an advantage in terms of modifying the taste which becomes brighter and more “tobacco-like” for a sheet made from bigger particles.

[0046] The invention also relates to a substrate produced according to the method as previously explained.

[0047] This substrate can comprise in dry basis: between 5 wt.% and 60 wt.% of an aerosol forming agent; between 0,3 wt.% and 5 wt.% of a thickening agent; between 10 wt.% and 70 wt. % of at one plant material.

[0048] It can also optionally comprise between 5 wt.% and 50 wt.% of a fiber material.

[0049] The invention also relates to an aerosol generating article comprising such a substrate.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The invention and its advantages will be better understood upon reading the following description, which is given by way of non-limiting examples and which is made with reference to the appended drawings, in which:

[0052] - Figure 1 is a schematic view of an aerosol generating assembly comprising an aerosol generating device and an aerosol generating article according to the invention;

[0053] - Figure 2 is a perspective view of the aerosol generating article of Figure 1 ;

[0054] - Figure 3 is a partially exploded perspective view of the aerosol generating article of Figure 1 , the aerosol generating article comprising a substrate; and

[0055] - Figure 4 is a flowchart of a method for producing the substrate of Figure 3.

[0056] DETAILED DESCRIPTION OF THE INVENTION Before describing the invention, it is to be understood that it is not limited to the details of construction set forth in the following description. It will be apparent to those skilled in the art having the benefit of the present disclosure that the invention is capable of other embodiments and of being practiced or being carried out in various ways.

[0057] As used herein, the term “aerosol generating device” or “device” may include a vaping device to deliver an aerosol to a user, including an aerosol for vaping, by means of a heater element explained in further detail below. The device may be portable. “Portable” may refer to the device being for use when held by a user. The device may be adapted to generate a variable amount of aerosol, e.g. by activating the heater element for a variable amount of time (as opposed to a metered dose of aerosol), which can be controlled by a trigger. The trigger may be user activated, such as a vaping button and / or inhalation sensor. The inhalation sensor may be sensitive to the strength of inhalation as well as the duration of inhalation to enable a variable amount of vapour to be provided (so as to mimic the effect of smoking a conventional combustible smoking article such as a cigarette, cigar or pipe, etc.). The device may include a temperature regulation control to drive the temperature of the heater and / or the heated aerosol generating substance (aerosol pre-cursor) to a specified target temperature and thereafter to maintain the temperature at the target temperature that enables efficient generation of aerosol.

[0058] As used herein, the term “aerosol” may include a suspension of vaporizable material as one or more of: solid particles; liquid droplets; gas. Said suspension may be in a gas including air. Aerosol herein may generally refer to / include a vapour. Aerosol may include one or more components of the vaporizable material.

[0059] Figure 1 shows an aerosol generating assembly 10 comprising an aerosol generating device 11 and an aerosol generating article 12. The aerosol generating article 12 is intended to operate with the aerosol generating device 11 to generate aerosol as it will be explained in further detail below.

[0060] According to the embodiment of Figure 1 , the aerosol generating device 11 comprises a device body 15 extending along a device axis Y between a closed end 16 and an open end 17. The open end 17 presents an opening from which the aerosol generating article 12 can be inserted inside the device 11. The device body 15 delimits an internal space of the device 11 receiving various elements designed to carry out different functionalities of the device 11. This internal space can for example receive a battery for powering the device 11 , a control module for controlling the operation of the device 11 , a heating chamber 60 for heating the aerosol generating article 12, etc. In the example of Figure 1 , only the heating chamber 60 is shown. Particularly, the heating chamber 60 is designed to receive at least partially the aerosol generating article 12. In the example of Figure 1 , the heating chamber 60 may be for example arranged adjacent to the opening formed by the open end 17 of the device body 15. The heating chamber 60 may for example extend according to the device axis Y and present a cup shape. The heating chamber 60 may comprise a heater designed to heat at least a part of the aerosol generating article 12. The heater comprises for example a pair of heating plates facing each other and designed to heat opposite walls of the aerosol generating article 12 as it will be explained in further detail below. Each heating plate may comprise metal or ceramics or be made from metal or ceramics. Metal is preferably stainless steel (e.g., SAE 316L). According to other embodiments, the heater comprises any other mean or material suitable for heating the aerosol generating article, as for example a heating blade or a magnetic coil interacting with a heat-inductive element next or in contact with the aerosol substrate.

[0061] In the example of Figure 2, the aerosol generating article 12 presents a flat shape. In other words, in this example, the aerosol generating article 12 is a flat-shaped cuboid extending along an article axis X between an inlet end 18 and an outlet end 19, and having external dimensions LxWxD. In a typical example, the length L of the article 12 according to the article axis X equals substantially to 33 mm while its width W and depth D are substantially equal respectively to 12 mm and 1 ,2 mm. According to different examples, the values L, W and D can be selected within a range of + / - 40%, for example. The depth D of the aerosol generating article 12 is formed by a pair of parallel walls 23A, 23B, called hereinafter lateral walls 23A, 23B, and the width W of the aerosol generating article 12 is formed by a pair of parallel walls 24A, 24B, called hereinafter wider walls 24A, 24B. Since in the example of Figure 2 the aerosol generating article 12 presents a flat shape, each wider wall 24A, 24B is for example at least 5 times, advantageously 10 times, wider than each lateral wall 23A, 23B. The flat shape of the aerosol generating article 12 is thus defined by the ratio between each wider wall 24A, 24B and each lateral wall 23A, 23B, which is greater than 5, advantageously greater than 10. In some embodiments, the edges between the wide and lateral walls 23A, 23B, 24A, 24B can be rounded. According to other examples, the aerosol generating article 12 can have any other suitable shape, for example a cylindrical shape (i.e. rod shape) having a circular or oval or rectangular cross-section. The aerosol generating article 12 comprises a substrate part 25 and a cooling part 26 arranged successively along the article axis X, as it is shown in Figures 2 and 3. The substrate part 25 may for example be slightly longer than the cooling part 26. For example, the length L2 of the substrate part 25 according to the article axis X may be substantially equal to 18 mm and the length L1 of the cooling part 26 according to the article axis X may be substantially equal to 15 mm. The substrate part 25 defines the inlet end 18 of the article 12 and the cooling part 16 defines the outlet end 19 of the article 12. The substrate part 25 and the cooling part 26 may be fixed one to the other by a wrapper 31 extending around the article axis X. In this case, the wrapper 31 forms the lateral and wider walls 23A, 23B, 24A, 24B of the aerosol generating article 12. The wrapper 31 can for example be formed of one or several paper sheets. In some embodiments, the aerosol generating article 12 is provided only with a substrate part 25.

[0062] The substrate part 25 of the aerosol generating article 12 is designed to be received (for example through the opening formed by the device body 15) in the heating chamber 60 of the aerosol generating device 11 so as the article and device axes X, Y coincides, as it is shown in Figure 1. The part of each wider wall 23A, 23B corresponding to the substrate part 25 of the article 12 is designed to be heated by the heating chamber 60 of the device 11. Particularly, according to some embodiments, each of these parts is designed to be in contact with the heating plate forming the heater, as explained above. In some embodiments, the corresponding part of only one of the wider walls 23A, 23B is designed to be heated by the heater. Still according to some other embodiments, at least a part of at least one of the walls 23A, 23B, 24A, 24B, is designed to be heated distantly (i.e. without contact) by the heater of the heating chamber 60, for example by convection.

[0063] The substrate part 25 comprises a substrate 35 shown in Figure 3. The substrate 35 extends according to the whole length of the substrate part 25 and forms a solid body which is able to release aerosol upon heating. This solid body can for example form a substantially cuboid shape. In some examples, the solid body forms on its surface aerosol channels conducting aerosol. In some examples, the solid body can have a corrugated shape in each its cross-section as shown in Figure 3. In this example, the corrugated shape defines a plurality of protruding regions and a plurality of valley regions. Each valley region forms an aerosol channel between its surface and an internal surface 36 of the wrapper 31. Each protruding region is in direct contact with the internal surface 36 of the wrapper 31. As it will be explained in further detail below, the substrate 35 comprises notably an active substrate comprising tobacco particles and / or inhalable agent, which contains at least one stimulant and / or flavour. The substrate 35 can be produced using a method explained in further detail below.

[0064] According to different embodiments, the cooling part 26 is designed to form itself a mouthpiece or be received inside an external mouthpiece mountable on the device body 15. The cooling part 26 is intended to act as a cooler to cool the vapour before it is inhaled by the user. In one embodiment, the cooling part 26 is hollow, advantageously entirely hollow. In other words, in this embodiment, the cooling part 26 is delimited only by the internal surface 36 of the wrapper 31. According to another embodiment, the cooling part 26 comprises at least one internal wall extending along the article axis X and forming one or several airflow channels. For example, the internal wall can be entirely adjacent to the internal surface 36 of the wrapper 31 or extend between a pair of walls, lateral or wider 23A, 23B, 24A, 24B. In this last case, several airflow channels can be formed in the cooling part 26. In still another embodiment, the cooling part 26 comprises a core. The core can have for example a corrugated shape and form one or several airflow channels. The core can be made of cellulosic material, such as corrugated paper or moulded pulp, or a combination of natural cellulosic material (e.g. paper) and acetate or polymer material. Still in another embodiment, the cooling part 26 is essentially made of acetate or polymer material and comprises voids to allow aerosol to flow through the part. This material can also act as a filter. In this case, the length L1 of the cooling part 26 can be reduced in comparison with other embodiments.

[0065] The method for producing the substrate 35 will now be explained with reference to Figure 4.

[0066] This method comprises a step 110 of forming a gel portion. This step 110 can comprise several sub-steps.

[0067] During a sub-step 112, a pre-mixture is formed by mixing an aerosol forming agent and a thickening agent. This pre-mixture advantageously forms a suspension.

[0068] The thickening agent may comprise a mixture of agar and carboxymethylcellulose (CMC) mixed in a ratio comprised between 10:90 and 90:10, preferably between 40:60 and 60:40, most preferably about 50:50. In some embodiments, other binding agents such as hydroxypropyl cellulose and guar gum, can also be used, preferably in combination with agar and / or CMC.

[0069] The aerosol forming agent can comprise glycerine, propylene glycol and / or any combination thereof. Preferably, the aerosol forming agent comprises or consists of glycerine.

[0070] During the next sub-step 114, the pre-mixture is heated to a temperature of at least 60°C, preferably between 65°C and 80°C.

[0071] During the next sub-step 116, water is added to the pre-mixture. This distributes evenly in the suspension the thickening and the aerosol forming agents.

[0072] Alternatively, the sub-step 116 of adding water is carried out before the sub-step 114 of heating the pre-mixture. In other words, in this case, water is first added to the pre-mixture and the pre-mixture is then heated.

[0073] In some embodiments, at the end of step 110, the gel portion can present the following content in wet basis:

[0074] The method can further comprise a step 120 of adding to the gel portion an active substrate portion to form the substrate dough. Particularly, the active substrate portion can comprise or can be formed by at least one plant material and / or fiber material and / or nicotine. The plant material can comprise leaf tobacco particles and / or non-tobacco botanical and / or extract of non-tobacco botanical. The fiber material can comprise cellulose fibers and / or citrus fibers. The plant material can be mixed with the fiber material in a ratio comprised between 3:1 to 6:1 , advantageously between 4:1 to 5:1. The leaf tobacco particles can be formed from tobacco leaves and / or tobacco lamina (i.e. destemmed tobacco leaves). In some embodiments, the leaf tobacco particles can have a size generally greater than a predetermined value. For example, the leaf tobacco particles can have the size D90 comprised between 120 pm and 5 mm, preferably between 500 pm and 900 pm and more preferably between 750 pm and 850 pm.

[0075] After mixing with the gel portion, the active substrate portion can form between 40 wt.% and 85 wt.%, advantageously between 50 wt.% and 75 wt.% and preferably between 60 wt.% and 70 wt.%, of the resulting mixture in wet basis. Accordingly, the gel portion can form between 15 wt.% and 60 wt.%, advantageously between 25 wt.% and 50 wt.% and preferably between 30 wt.% and 40 wt.%, of the resulting mixture in wet basis.

[0076] The method can further comprise a step 130 of forming the substrate 35 from the substrate dough. For example, the substrate 35 can present a solid body or bodies. The or each body can present a sheet, one or several strips, one or several threads, and / or one or several beads. Advantageously, the step 130 comprises laminating the substrate dough into a plurality of sheets.

[0077] This step 130 can be performed using an embossing / debossing process or a stamping process or a molding process. A combination of these processes can also be used. Alternatively or additionally, processes for forming dough substrate including extrusion of slabs or chunks and subsequent lamination, can be used. The process can also include forming aerosol channels, as explained above. Examples of reconstituted tobacco forming processes starting from a reconstituted tobacco dough are described in W02020058814, WO2021181327 or WO2021144676.

[0078] Optionally, the step 130 further comprises drying at least partially the solid body or bodies reduce or eliminate the water content. A partial drying can for example be used for some particular shapes of the substrate 35. For example, for a substrate having a flat shape, the initial water content comprised between 9 wt.% and 12 wt.% can be reduced to a value comprised between 6 wt.% to 9 wt.%. In some embodiments, at the end of step 130, the substrate 35 can present the following content in dry basis: In some embodiments, the substrate 35 can further be cut to fit the dimensions of the aerosol generating article 12, as previously disclosed.

Claims

CLAIMS1. A method for producing a substrate (35) for an aerosol generating article (12) adapted to operate with a heat-not-burn aerosol generating device (11), the method comprising:- forming (110) a gel portion: by forming (112) a pre-mixture of an aerosol forming agent and a thickening agent; by heating (114) the pre-mixture; by adding (116) water to the pre-mixture;- adding (120) to the gel portion an active substrate portion to form a substrate dough.

2. The method according to claim 1 , wherein the pre-mixture is heated (114) before adding (116) water to the pre-mixture.

3. The method according to claim 1 or 2, wherein the gel is formed by mixing:- between 80 wt.% and 96 wt.%, preferably 90 wt.%, of the aerosol forming agent;- between 1 wt.% and 10 wt.%, preferably 5 wt.%, of the thickening agent;- between 1 wt.% and 10 wt.%, preferably 5 wt.%, of water.

4. The method according to any one of the preceding claims, wherein the thickening agent comprises a mixture of agar and Carboxymethylcellulose (CMC) mixed in a ratio comprised between 10:90 and 90:10, preferably between 40:60 and 60:40, most preferably about 50:50.

5. The method according to any one of the preceding claims, wherein the pre-mixture of the aerosol forming agent and the thickening agent forms a suspension.

6. The method according to any one of the preceding claims, wherein the pre-mixture is heated to a temperature of at least 60°C, preferably between 65°C and 80°C.

7. The method according to any one of the preceding claims, wherein it further comprises forming (130) a substrate (35) from the substrate dough and optionally, drying the substrate (35); advantageously, the substrate (35) presenting a solid body or bodies, preferably a sheet, strips, threads, or beads.

8. The method according to claim 7, wherein the substrate (35) has a water content between 9 wt.% and 12 wt.% and is optionally dried to reduce its water content between 6 wt.% to 9 wt.%.

9. The method according to claim 7 or 8, wherein the substrate (35) is laminated into a sheet, preferably before drying.

10. The method according to any one of the preceding claims, wherein the substrate (35) contains between 30 wt.% and 50 wt.% of the aerosol forming agent in dry basis.

11. The method according to any one of the preceding claims, wherein the active substrate portion comprises or is formed by at least one plant material and / or fiber material and / or nicotine.

12. The method according to claim 11 , wherein the at least one plant material is mixed with the fiber material in a ratio comprised between 3: 1 to 6:1.

13. The method according to claim 11 or 12, wherein the at least one plant material comprises leaf tobacco particles and / or non-tobacco botanical or extract of non-tobacco botanical.

14. The method according to any one of claims 11 to 13, wherein the tobacco particle size D90 is comprised between 120 pm and 5 mm, preferably between 500 pm and 900 pm.

15. A substrate (35) produced according to the method according to any one of the preceding claims, comprising in dry basis: between 5 wt.% and 60 wt.% of an aerosol forming agent; between 0,3 wt.% and 5 wt.% of a thickening agent; between 10 wt.% and 70 wt. % of at one plant material.

16. The substrate (35) according to claim 15, further comprising between 5 wt.% and50 wt.% of a fiber material.

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