DESC:
TECHNICAL FIELD OF THE INVENTION

[001] The present subject matter described herein, in general, relates to an aerosol generating articles and in particular, relates to aerosol generating substance wherein the aerosol generating substance is made to have better and visibly denser aerosol release.

BACKGROUND OF THE INVENTION

[002] Electrically heat not burn aerosol generating systems are well known in the prior art. This system includes an aerosol generating device and an aerosol generating article. The aerosol generating device may have a heating element, a controller to control the temperature of the heating element and a power source. The aerosol generating article may include an aerosol generating substrate attached with other parts which makes the complete aerosol generating article.

[003] The aerosol generating substrate may be a gathered sheet of reconstituted tobacco or other plant-based materials design to deliver specific sensorial attributes. The gathers sheet of the reconstituted tobacco is formed in the form of a tubular cylinder wrapped with a wrapping paper.

[004] The gather sheet of reconstituted tobacco may be made by casting the aqueous solution which may include finely ground tobacco powder, aerosol generating chemicals, a binder and fibres. The aerosol generating chemicals can be from any of the polyhydric alcohols such as glycerine, polyethylene glycol, etc. The binding material may be a cellulose derivative such as Carboxymethyl cellulose, Hydroxypropyl methyl cellulose, guar gum and its derivatives, etc. The fibre material can be a cellulose fibre.

[005] The aerosol generating substrate might be attached to a cooling segment and a filter segment to form the overall aerosol generating article. The aerosol generating article can also be made by cut the reconstituted tobacco sheet or tobacco leaf, substantially aligning those in the longitudinal axis of the tubular cylinder and wrap with the wrapping paper.

[006] The heating of the aerosol generating article and releasing of aerosol can be done by inserting the aerosol generating article inside the cavity of the device. The heater might be of resistive heating or induction heating and the heater can be in the form of a flat substrate or a needle type which pierce the aerosol generating substrate. The heater can be in the form of a tubular cylinder which can encompass the aerosol generating substrate.

[007] People known for using this kind of aerosol generating system are well aware that there is a waiting time before the first puff and depending upon the technology, the waiting time can vary from 20 seconds to 40 seconds. This waiting time is normally called as ‘pre-heating’ time. The ‘pre-heating’ time is required to transfer the required amount of heat to a substantial part of the tobacco to generate perceivable aerosol. This waiting time is due to the lower thermal conductivity of the tobacco particle and the air channel formed between the fold of the sheet during gathering the sheet in the form of a rod. It is believed that, while heating, glycerine, nicotine, water and other volatile components turned into a vapor phase and when temperature drops, the vapor forms aerosol. The size of the aerosol depends on a mixture of complex factors including the ratio of water and glycerine, the presence of any other steric hindrance forming chemicals, etc. If larger droplets are formed inside the aerosol generating article, they might coalescence and filter out. While smaller droplets can pass though the filter, cools faster and generates denser aerosol when exhaled.

[008] It is well known that consumer loves higher volume and dense cloud while exhaling. They relate this with satisfaction and value for money. Device designers are trying to fill the unmet need by either increasing the ‘pre-heating’ time or increasing the heating temperature. Some of the device manufacturers are offering multiple heating modes in their device. These techniques are good to increase aerosol volume but in most of the cases consumers are not satisfied with longer waiting time or burning lips and throat with the hotter aerosol coming due to higher temperature.

[009] Efforts are put to overcome such serious limitation by addition of higher percentage of aerosol generating chemicals, such as glycerine, in the reconstituted tobaccoHowever, presence higher percentage of such hygroscopic chemicals might leads to higher tendency of moisture absorption and spoilage of the product. It is also observed that the product tends to generate hotter aerosol if the percentage of moisture in the tobacco is higher.

[0010] The inventors have also noticed that more than half of the glycerine remain in the aerosol generating substrate post consumption and with a closer look, it has been found that the major portion of the glycerine is released from the areas closer to the heater.

[0011] Increasing thermal conductivity of the aerosol generating substrate is believed to be another way to increase aerosol formation. In EP3090639A1, the patent discloses thermally conductive rods that are formed from a first sheet comprising an aerosol-forming material and a second sheet comprising a thermally-conductive material, the first and second sheets being gathered together and circumscribed by a wrapper. The rod may be used as a component part of an aerosol-generating article. Aerosol-formers and humectants for inclusion in sheets of homogenised tobacco material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1,3-butanediol and glycerine; 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 second sheet is a metal foil and carbon foil.

[0012] Commercially available aerosol generating articles, because of their lower thermal conductivity, cannot be heated rapidly to the desired temperature and hence the waiting time of the first puff is either longer or the aerosol volume of the first puff is lesser.

[0013] US20190090537A1 describes an elongate smoking article having a lighting end, an opposed mouth end and a tobacco portion disposed between the lighting end and the mouth end portion. It further describes that a combustible fuel element adapted for use in a smoking article is provided, the fuel element comprising a combustible carbonaceous and a particulate ignition aid dispersed throughout the fuel element. The particulate ignition aid is advantageously non-catalytic and include metals, metal oxides, inorganic salts, and mineral acids. The ignition aid enhances the operation of the fuel element by reducing the amount of time required to ignite the fuel element.

[0014] US20200060341A1 discloses an aerosol delivery device configured to yield an inhalable substance. It comprises a control body, a heating member, a control component located within the control body, a power source, and a removable aerosol source member that includes a substrate portion. The substrate portion may include a continuous thermally conductive framework integrated with an aerosol forming material, which framework enhances heat transfer from the heating member to the aerosol forming material. In some implementations, the continuous thermally conductive framework may comprise a coil integrated with a substantially cylindrical aerosol forming material. It further discloses that the thermally conductive framework comprises at least one of a metal material, a coated metal material, a ceramic material, a carbon material, a polymer composite, and any combination thereof.

[0015] US20190261685A1 discloses an aerosol generating substrate comprising a fibrous filler material; an aerosol forming material; and a plurality of heat conducting constituents. In an embodiment, the aerosol generating substrate is a sheet and the heat conducting constituents are incorporated within the sheet in granular form, a powder form, a fiber form, a mesh form, and a fiber cloth form. The material of the heat conducting constituents comprises at least one of a metal material, a metal alloy material, a ceramic material, a carbon material, and a polymeric fiber material coated with a metal material.

[0016] The prior art teaches the use of thermally conductive material such as metal particle and higher thermal conductive ceramic material to increase thermal conductivity of the aerosol generating article. Use of thermally conductive materials to increase thermal conductivity of the substrate is well known in the art. However, the prior art also failed to explain the method of using these thermal conductive materials to extract aerosol from the aerosol generating substrate.

[0017] The reconstituted tobacco sheet is made by drying the casted formulation into sheet. The sheet is normally in the range of 100 microns to 200 microns. At the time of gathering the sheet to form a rod like structure, longitudinal air channel forms between the sheet. Hence, the inventors of the present invention found that it is required to design a reconstituted sheet which has improved thermal conductivity not only in sheet plane (X-Y plane) but also in Z plane. The inventors of the present invention surprisingly found that the substantially spherical and rod shaped thermally conductive material with different aspect ratio can be align effectively in the reconstituted tobacco sheet to form the network with lesser percentage of inclusion of these materials to effectively improve aerosol generation.

OBJECT OF THE INVENTION

[0018] Accordingly, it is an object of the present invention to increase aerosol generation in the initial puffs and remained consistent till the last puff by developing a network of thermally conductive materials having different shape and aspect ratio with minimum inclusion percentage.

[0019] It is a further object of the present invention to provide an aerosol generating substrate comprising two thermally conductive material wherein the first thermal conductive material has higher thermal conductivity than the second thermal conductive material.

[0020] It is a yet another object of the present invention to provide an aerosol generating substrate comprising thermally conductive material is an inorganic material, with a thermally conductivity is not less than 5 W/m-k, particle size, not less than 5 microns, bulk density not more than 5.5 gm/cc and thermal stability of not less than 500 0C.

[0021] It is further objective of the present invention to provide an aerosol generating substrate having at least one thermally conductive inorganic material having aspect ratio not less than 100.

[0022] It is further objective of the present invention to provide an aerosol generating substrate comprising a mixture of thermally conductive inorganic material wherein at least one of the thermally conductive material as aspect ratio more than 100 and wherein at least one of the thermally conductive material is substantially spherical in shape.

[0023] It is further objective of the present invention to provide a recipe with the thermally conductive material which is compatible and processable with the existing system.

[0024] It is further objective of the present invention to include long chain alcohols in the aerosol generating substrate having vaporization temperature well within the operating temperature and helps to increase denser exhale cloud formation. The long chain alcohol can be added in the sheet making formulation or as post processing of the dried sheet.

SUMMARY OF THE INVENTION

[0025] The following disclosure presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0026] Without limitation, the present invention discloses the use of thermally conductive material having a mixture of different aspect ratio and thermal conductivity in the aerosol generating substrate formation to extract more aerosol with less than 5 % w/w inclusion.

[0027] The present invention also discloses the use of long chain alcohols such as Gurbeit Alcohols, along with glycerine to synergistically increase the aerosol generation.

[0028] Thus in accordance with an aspect of the present invention, there is provided an aerosol generating substrate for an aerosol generating article wherein the aerosol generating substrate is formed by gathered sheet of aerosol generating material and at least two thermally conductive material wherein the first material has higher thermal conductivity than the second material and one thermally conductive material is substantially spherical in shape and the other thermally conductive material is substantially rod or plate shaped and at least one aerosol generating agent and a combination thereof.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0029] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0030] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0031] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0032] Described herein are aerosol generating articles and methods of making said articles. Aerosol delivery devices or aerosol generating articles comprise a heated end and a mouth end, a heating source, a control unit and an aerosol generating article. The aerosol generating source comprises an aerosol generating substrate. Particularly described are aerosol generating substrates including thermally conductive materials which improve the aerosol generation with higher aerosol density.

[0033] The inventors have found that better aerosol generation happens when more than one type of thermal conductive material having different shape and size are added in the sheet wherein the first material have higher thermal conductivity than the second material and having different aspect ratio. The inventors of the present invention believe that inclusion of substantially spherical thermal conductive material and rod like material can create a network of thermally conductive material in the machine direction (X-Y plane) and perpendicular to the machine direction (Z plane) and this kind of network can help to generate better aerosol when uses as substrate in the aerosol generating article. It is also believed that, the rod-shaped material forms a bridge between the substantially spherical material and helps to transfer energy quickly in all direction rather than using only spherical materials where the gap between the spherical material does not allow quicker conduction.

[0034] Accordingly, the present invention provides an aerosol generating article comprising:
at least one aerosol former and at least two thermally conductive material.

[0035] Thermally conductive materials are selected from thermally conductive ceramics and other inorganic materials like Boron Nitride, Zinc Oxide, Magnesium Oxide, Alumina, Talc and the like.

[0036] An aerosol generating substrate comprises tobacco or non-tobacco materials like tobacco shreds, tobacco strips, a tobacco cast sheet, reconstituted tobacco material, or combinations thereof, and/or a mix of finely ground tobacco, tobacco extract, spray dried tobacco extract, or other tobacco form mixed with aerosol formers.

[0037] Further described herein is an aerosol generating substance wherein the aerosol generating substrate has a combination of glycerin and another aerosol generating chemical. The aerosol generating chemical has other functional groups such as esters. The aerosol generating chemical has longer chain or branched chains. The aerosol generating chemicals have boiling point lower than 350-degree C.

[0038] These alternate aerosol generating agents are less hygroscopic and hence have a lower rate of moisture absorption (from the surroundings), hence it increases the shelf life of the product. These alternate aerosols generating chemical improves the density of the exhale aerosol.

[0039] The present inventors surprisingly found that a mixture of glycerin and Guerbet alcohol having different chain length synergistically improves the exhale aerosol density. Preferably, such alcohol is selected from compounds having boiling point lower that the operating temperature of the heating device such as 2-Hexyl-1-nonanol, 2-octyl-1-dodecanol, 2-decyl-1-tetradecanol and the like.

[0040] The present inventors found that higher thermally conductive spherical materials when mixed with rod (or plate) like (higher aspect ratio) thermally conductive material and used in the formation of the sheet (less than 200 micron), produces a network of higher thermal conductive materials in the matrix. The inventors found that the thermally conductive material can not be added the way it has been added in plastics and other applications where the inclusion of thermal conductive material can be as high as 30 %. The present inventors have observed that by using a mixture of thermal conductive material having spherical and/or rod like structure a network of filler material having proximity of both kind of particles can be made with minimum filler inclusion hence the thermal conductivity across all direction can be improved.

[0041] The thermally conductive ceramic /inorganic material with thermal conductivity not less than 5 W/m-K. Preferably the particle size not less than 5 microns. The bulk density of the material is not more than 5.5 gm/cc.

[0042] The thermally conductive material having aspect ratio not less than 100.

[0043] It was surprisingly found that when thermally conductive materials such as Boron Nitride, Zinc Oxide, Magnesium Oxide, Alumina, Talc and the like when added with higher thermal conductivity is mixed in an aerosol generating substrate composition, it improves the overall aerosol generating with higher aerosol density. These kinds of thermally conductive materials are stable at operating temperature hence do not change its physical and chemical properties.

[0044] In the present invention, the inventors also use a mix of different particle size and different aspect ratio to increase thermal conductivity of the overall product.

[0045] These kinds of thermally conductive materials can be easily processed along with the existing recipe hence do not need to change the mixing and other processing parameters.

[0046] This matrix is capable to conducting heat faster in all direction hence can form higher percentage of aerosols compare to the control product with no such high thermal conductive material. In most of the cases where such thin sheets are formed (less than 200 micron), only higher thermal conductive material – spherical and/or plate (or rod ) type of structure can either increase the thermal conductivity of the matrix in X-Y plane or in Z plane whereas for the faster and consistent aerosol extraction, an increase thermal conductivity of the matrix in all direction is needed. The present inventors found that it can be possible by increasing the percentage of any of the spherical or plate type material but this will either affect the processing of the matrix or the formation of substrate besides increasing the cost.

[0047] By using mixture of spherical and/or rod like thermally conductive material and at not more than 2 % w/w level, there is enough thermal conductivity in all direction sufficient enough the produce increased aerosol in initial puff and remained consistent till the last puff.

[0048] In an example of preparation of the aerosol generating sheet,

1. Mixing of: Ground tobacco (matrix material) + binder + Triacetin + Mixture of thermally conductive materials
2. Hydration with water
3. Mixing of pulp, water and aerosol forming chemicals
4. Hydration
5. Sheet formation and drying
6. Final sheet in roll form

Example 1
Preparation of an aerosol generating sheet
In an example of preparing the aerosol generating sheet, the tobacco is ground to make a powder having at least 50 % of the particle with particle size less than 50 microns. The tobacco powder is mixed with carboxymethyl cellulose, triacetin, guerbet alcohol, thermal conductive materials and other solid ingredients in a ribbon blender.
In a separate tank, glycerin is mixed with water and micro fibrillated cellulose fiber and agitate to make a homogeneous mixture.
The powder and aqueous slurry are fed into a high shear mixing tank to make homogeneous slurry. The slurry is also passed through online homogenizer to have a better dispersion of the particles in the slurry. The final slurry is casted on the metal conveyor and dries with multi stage hot air dryer. The dry reconstituted tobacco sheet is then wound as bobbin for future use.
[0049] Comparative example

Parameters Sample A Sample B Sample C
Recipe Control -without thermally conductive material With 2 % Boron Nitride -spherical granules (size: 50 micron) With 1.5 % Boron Nitride -spherical granules (size: 50 micron) + 0.5 % Talc (aspect ratio>500)
Thermal conductivity 0.23 0.35 0.35
Aerosol volume (Smoke panel) Good Better Best
Aerosol density
(Smoke panel) Good Better Best
Overall satisfaction
(Smoke panel) Good Better Best

,CLAIMS:1. An aerosol generating substrate for an aerosol generating article, wherein the aerosol generating substrate is formed by gathered sheet of aerosol generating material and at least two thermally conductive material wherein the first material has higher thermal conductivity than the second material and one thermally conductive material is substantially spherical in shape and the other thermally conductive material is substantially rod or plate shaped and at least one aerosol generating agent and a combination thereof.

2. The aerosol generating substrate as claimed in claim 1, wherein the said substrate is a mixture of glycerin and other long chain alcohol such as Guerbet alcohol.

3. The aerosol generating substrate as claimed in claim 2, wherein Guerbet alcohol is selected from alcohols having boiling point below the operating temperature of the device such as 2-Hexyl-1-nonanol, 2-octyl-1-dodecanol, 2-decyl-1-tetradecanol and the like.

4. The aerosol generating substrate as claimed in claim 1, wherein the material having higher conductivity is selected from inorganic materials such as boron nitride, alumina, silicon carbide and the like.

5. The aerosol generating substrate as claimed in claim 1, wherein the material having lower conductivity is an inorganic material, with a thermally conductivity of not less than 5 W/m-k and particle size not less than 5 microns and a bulk density of not more than 5.5 gm/cc.

6. The aerosol generating substrate as claimed in claim 5, wherein the material having lower conductivity is selected from Zinc Oxide, Magnesium Oxide, , Talc and the like.

7. The aerosol generating substrate as claimed in claim 1, wherein the material having higher conductivity is spherical in shape.

8. The aerosol generating substrate as claimed in claim 1, wherein the material having lower conductivity is rod like and/or plate like in shape and has higher aspect ratio.

9. The aerosol generating substrate as claimed in claim 1 wherein the thermally conductive material is a mixture of spherical and/or rod like thermally conductive material and is present in an amount of not more than 2 % w/w.

10. The aerosol generating substrate as claimed in claim 1 wherein the ratio of glycerin to guerbet aerosol is in the range to 80:20, more preferably in the ratio of 85:15 and most preferably 90:10.

11. The aerosol generating substrate as claimed in claim 1 further comprising tobacco or non-tobacco materials.

12. The aerosol generating substrate as claimed in claim 1 further comprising a binder selected from cellulose and its derivative, guar gum and its derivatives and the like.