Method for producing an aerosol generating sheet with solid plant material

Abstract

Method for producing an aerosol generating sheet with solid plant material The method of producing an aerosol generating sheet comprises mixing the solid plant material with water, aerosol former and a binder to form a paste, wherein: - the paste contains long fibres having an average length above 400 µm, - the paste has a water content of less than 50 wt.%, and - the paste is extruded in an extruder and - the paste is kneaded one or more kneading zones of the extruder.

Description

[0001] Method for producing an aerosol generating sheet with solid plant material

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of producing an aerosol generating sheet using a paste containing solid plant material mixed with water, aerosol former and binder.

[0004] BACKGROUND OF THE INVENTION

[0005] 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.

[0006] Available reduced-risk or modified-risk devices are so called “aerosol generating devices” or “heat-not-burn devices” which are configured to heat vaporizable materials as opposed to burning tobacco in conventional tobacco products.

[0007] Such an aerosol generating device is configured to generate aerosol or vapour by heating an aerosol generating substrate that is usually comprised in a consumable article separate from the aerosol generating device.

[0008] The aerosol generating substrate contains for example moist tobacco leafs or other suitable vaporizable material that vaporizes at a temperature typically in the range of 150°C to 350°C.

[0009] Heating an aerosol generating substrate, without combusting or burning it, releases aerosol that comprises the components sought by the user but not by-products of combustion and burning. Furthermore, the aerosol produced by heating the vaporizable material contained in the aerosol generating substrate does not comprise the typical 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. US20220346433A1 discloses a method of producing an aerosol generating material, the method comprising successively mixing tobacco powder and plant powder with a binder gel to obtain a tobacco paste, extruding the tobacco paste to obtain an extruded profile, fractioning the extruded profile into portions of tobacco paste, forming and rolling a web of tobacco paste, drying the web of tobacco paste and using the web of tobacco paste to form an aerosol generating substrate.

[0010] The presence of long fibers in the solid plant material used for producing the aerosol generating material may create the so-called issue of “fiber spots”, i.e. the presence of fiber aggregates in a laminated sheet produced with the solid plant material, such fiber spots generating from time to time stops of the production line used for producing the aerosol generating material.

[0011] SUMMARY OF THE INVENTION

[0012] One of the aims of the invention is to provide a method of producing an aerosol generating sheet which is easy and cost effective to implement and can accommodate more easily the presence of long fibers in the aerosol generating sheet, in particular by mitigating the occurrence of fiber spots and preventing the disruption of the production of the aerosol generating sheet.

[0013] To this end, the invention proposes a method for producing an aerosol generating sheet in which solid plant material is mixed with water, aerosol former and a binder to form a paste, wherein:

[0014] - the paste contains long fibres having an average length above 400 pm,

[0015] - the paste has a water content of less than 50 wt.%, and

[0016] - the paste is extruded in an extruder, and

[0017] - the paste is kneaded in one or more kneading zones of the extruder.

[0018] Preferably, the paste is formed before extruding to a water content comprised between 20 wt.% and 45 wt.%, most preferably between 30 wt.% and 40 wt.%. Such water content enables the paste to have a proper solid texture which facilitates kneading and further handling during its subsequent transformation into a sheet. Each kneading zone (or kneading section) is provided in a section of the extruder, i.e. in a portion of length of the extruder. Each kneading zone replaces for example a section of one or more conveying screw elements of the extruder.

[0019] The kneading of the paste will lead to kneading and so dispersing long fibers present in the paste thereby reducing the occurrence of fiber spots in the aerosol generating sheet produced from the paste.

[0020] The provision of one or more kneading zones in the extruder allows an easy and cost effective implementation of the method by adapting an extruder, in particular an extruder of an already existing installation, by providing kneading elements on one or more rotors of the extruder for defining the one or more kneading zones.

[0021] The aerosol laminated sheet is suitable as a ground material for manufacturing an aerosol generating substrate, e.g. for insertion in a consumable article for use in an aerosol generating device.

[0022] In some examples, the extruder comprises one or more conveying zones configured for conveying the paste along the extruder, each conveying zone being distinct from each kneading zone.

[0023] Each conveying zone (or conveying section) is provided in a section of the extruder, i.e. in a portion of length of the extruder. Each conveying zone comprises for example one or more conveying screw elements.

[0024] Each conveying zone is located in a section of the extruder distinct from the section of each of the one or more kneading zone.

[0025] The presence of one or more conveying zones allows conveying the paste along the extruder, in particular forcing the paste to move from an inlet of the extruder to an outlet of the extruder.

[0026] The presence of one or more kneading zones specifically configured for kneading the paste allows implementing an efficient kneading of the paste and thus of the fibers. In some examples, the one or more conveying zones comprises an inlet conveying zone located along the extruder between an inlet of the extruder and the one or more kneading zones of the extruder.

[0027] The inlet conveying zone located between the inlet of the extruder and the one or more kneading zones ensures that the paste is pushed from the inlet and through the kneading zone. The inlet conveying zone is adjacent the inlet of the extruder and is preferably the most upstream zone of the extruder.

[0028] In some examples, the one or more conveying zones comprises an outlet conveying zone located along the extruder downstream the one or more kneading zones of the extruder and outlet of the extruder.

[0029] The outlet conveying zone located downstream the one or more kneading zones ensures that the paste is pushed towards the outlet of the extruder. The outlet conveying zone is adjacent the outlet of the extruder and is preferably the most downstream zone of the extruder.

[0030] In some examples, the extruder comprises two or more kneading zones distributed along the extruder, preferably three or more kneading zones distributed along the extruder.

[0031] A plurality of kneading zones allows kneading the paste several times and / or with different kneading parameters. Kneading parameters include for example a maximum pressure of the paste inside the kneading zone.

[0032] In some examples, the two or more kneading zones are spaced along the extruder. In other word, each preceding kneading zone is separated from the next kneading zone from a non-zero distance along the extruder.

[0033] In some examples, the one or more conveying zones comprises at least one intermediate conveying zone, each intermediate conveying zone being located along the extruder between two kneading zones.

[0034] In some examples, each preceding kneading zone is separated from the next kneading zone by an intermediate conveying zone. The provision of a conveying zone between two successive kneading zones (a preceding kneading zone and the next kneading zone) allows separating the kneading processing performed on the paste by the two successive kneading zones with conveying the paste along the extruder to feed the paste from the preceding kneading zone to the next kneading zone with appropriate feeding parameters. Feeding parameters comprises for example the pressure of the paste.

[0035] In some examples, the one or more conveying zones alternate with the one or more kneading zones along the extruder, preferably with an inlet conveying zones located between the inlet of the extruder and the one or more kneading zones and / or an outlet conveying zones located between the one or more kneading zones and the outlet of the extruder provided with the die.

[0036] In some examples, the paste is kneaded in each kneading zone by kneading elements which are mounted rotatable about a rotation axis aligned or parallel to an extrusion axis of the extruder.

[0037] Preferably, the kneading elements are configured to compress the paste perpendicularly to the extrusion axis upon rotation of the kneading elements about the rotation axis.

[0038] In some examples, the paste is conveyed in the one or more conveying zones by at least one conveying screw element. The conveying screw element is rotatable about a screw axis aligned or parallel to the extrusion axis.

[0039] The extruder comprises for example one or more rotors, each rotor being rotatable about a rotation axis parallel to the extrusion axis, a conveying screw element being provided on each rotor in each conveying zone and / or one or more kneading elements being provided on each rotor in each kneading zone.

[0040] The one or more rotor each provided with a screw element in each conveying zone and one or more kneading elements in each kneading zone allows performing both the kneading and the conveying and thus the extrusion simply by driving the rotor about its rotation axis.

[0041] In some examples, the rotor comprises one single rotor or two parallel rotors. In some examples, the paste is extruded into paste portions, such as slabs and / or pellets and / or chunks, the paste portions being then laminated in a calendaring unit for obtaining the laminated sheet.

[0042] In some examples, the paste is fractioned into paste portions at the outlet of the extruder by a fractioning unit.

[0043] In some examples, the outlet of the extruder is defined by an end of a barrel of the extruder or a die provided at the end of such barrel.

[0044] In some examples, the calendaring unit comprises successive calendaring stations, preferably between three and five calendaring stations, most preferably four pairs of calendaring stations, the calendaring stations having decreasing clearances in a conveying direction. Each calendaring station comprises for example one roller or a pair of rollers defining the laminating gap of the calendaring station.

[0045] In some examples, the laminated sheet is laminated to a defined thickness comprised between 80 pm and 400 pm.

[0046] Performing kneading in the extruder allows a good integration of the fibers in the paste which in turns allows obtaining a laminated sheet with a good tensile strength.

[0047] In some examples, the tensile strength of the laminated sheet is more than 2.5 N / mm2, preferably more than 3.0 N / mm2, more preferably more than 3.5 N / mm2. In some examples, the tensile strength of the laminated sheet is around 3.7 N / mm2.

[0048] In some examples, the paste contains fibres having an average length comprised between 400 pm and 2500 pm, preferably between 600 pm and 1500 pm, more preferably between 800 pm and 1200 pm.

[0049] The amount of fibres is preferably between 2 wt.% to 10 wt.% in dry weight, more preferably between 3 wt.% to 9 wt.%, most preferably 4 wt.% to 8 wt.%., for example 6 wt.%. The controlled amount of long fibres participate to the improvement of the mechanical properties, e.g., tensile strength, of the sheet and so the reduction of manufacturing problems (e.g., disruptions due to breakage) in the rod making process. In some examples, the solid plant material comprises ground leaf tobacco. Ground leaf tobacco may preferably comprise a majority of tobacco lamina (in weight).

[0050] In some embodiments, the content of ground leaf tobacco in the paste is comprises between 60% and 80% in dry mass.

[0051] In some examples, leaf tobacco is ground to a particle size (D90) comprised between 80 pm and 1500 pm before mixing to form the paste.

[0052] In some examples, the long fibres comprise primarily non-tobacco fibres and / or cellulose fibres. The long fibres may also be formed from tobacco stems and / or stalks.

[0053] In some examples, the binder comprises: cellulose derivative, cellulose ester, cellulose ethers, plant-derived polysaccharide, algae-derived polysaccharide, microorganism-derived polysaccharide, crustacea-derived polysaccharide, starch, protein, polyphosphoric acid, sodium polyacrylate, polyvinylpyrrolidone and combinations thereof.

[0054] In some examples, the binder comprises: methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxymethyl ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, benzyl cellulose, trityl cellulose cyanoethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, cellulose ester(s), guar gum, tara gum, locus bean gum, tamarind seed gum, pectin, gum arabic, gum tragacanth, gum karaya, gum ghatti, arabinogalactan, flaxseed gum, cassia gum, psyllium seed gum, artemisia seed gum, carrageenan, agar, alginic acid, propylene glycol alginate, furcellaran, Gloiopelfis furcata extract, xanthan gum, gellan gum, curdlan pullulan, Agrobacterium succinoglycan, welan gum, Macrophomopsis gum, rhamsan gum, chitin, chitosan, glucosamine, starch glycolate, pregelatinized starch, dextrin, wheat gluten, rye gluten and combinations thereof.

[0055] In some examples, the aerosol former comprises: polyhydric alcohols, such as triethylene glycol, 1,3-butanediol and glycerine; ester of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic ester of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols such as triethylene glycol 1,3-butanediol and most preferred, glycerine, propylene glycol and combinations thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] 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:

[0057] - Figure 1 illustrates an installation for implementing a method of producing an aerosol generating material;

[0058] - Figure 2 is a cross-sectional view of a an extruder of the installation of Figure 1 , taken along line II - II on Figure 1 to illustrate a kneading zone of the extruder;

[0059] - Figure 3 is block diagram illustrating steps of the method of producing an aerosol generating material.

[0060] DETAILED DESCRIPTION OF THE INVENTION

[0061] 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.

[0062] 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 heating oven 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. The device may include a temperature regulation control to drive the temperature of the heating oven and / or the vaporizable material (aerosol pre-cursor) to a specified target temperature and thereafter to maintain the temperature at the target temperature that enables efficient generation of aerosol. As used herein, the term “aerosol” may include a suspension of vaporizable material as liquid droplets and / or 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.

[0063] As used herein, the term “vaporizable material” may refer to a smokable material which may for example comprise nicotine or tobacco and an aerosol former. Tobacco may take the form of various materials such as shredded tobacco, granulated tobacco, tobacco leaf and / or reconstituted tobacco. Suitable aerosol formers include: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, acids such as lactic acid, glycerol derivatives, esters such as triacetin, triethylene glycol diacetate, triethyl citrate, glycerin or vegetable glycerin. In some embodiments, the aerosol generating agent may be glycerol, propylene glycol, or a mixture of glycerol and propylene glycol. The substrate may also comprise at least one of a gelling agent, a binding agent, a stabilizing agent, and a humectant.

[0064] The installation 2 illustrated on Figure 1 is configured for forming a paste P containing solid plant material PM mixed with water W, aerosol former AF and binder B and for processing the paste P such as to obtain an aerosol generating sheet. The paste is formed to a water content of less than 50 wt.%, preferably a water content comprised between 20 wt.% and 45 wt.%, most preferably between 30 wt.% and 40 wt.%.

[0065] The components may be mixed to form the paste in many different orders. For example, the solid plant material PM, water W, aerosol former AF and binder B may be assembled all at once and mixed. In another example, the solid plant material PM such as tobacco powder and non-tobacco fibres may be premixed to provide a dry mix and the dry mix may be subsequently mixed with a wet solution including water W, binder B and aerosol former AF. In another example, the non-tobacco powder may be premixed with water W and / or aerosol former AF and mixed with tobacco power.

[0066] In an example, in a first a gel portion is prepared by mixing the aerosol former AF and the binder B with the aid of the mixer. Water W is added to the gel mixture in a second step to avoid clumping in the liquid portion making dosing and mixing of the components easier. Water can be added to the gel portion under continuous agitation. Finally, the liquid portion is mixed to the solid tobacco plant PM. The solid tobacco plant may include tobacco powder optionally with non-tobacco fibres e.g. cellulose fibres. The installation 2 comprises for example a mixing unit 4 configured for mixing the solid plant material PM with water W, the aerosol former AF and the binder B, thus forming the paste P. The mixing unit may comprise a Turbo mixer and the like.

[0067] The installation 2 comprises an extruder 6 configured to extrude the paste P. The extruder 6 extends along an extrusion axis A between an extruder inlet 6A configured for receiving the paste P to an extruder outlet 6B.

[0068] The extruder 6 comprises a barrel 10 defining an internal chamber 12 extending axially along the extrusion axis A from the extruder inlet 6A to the extruder outlet 6B.

[0069] The extruder 6 comprises one or more rotors 14 extending in the chamber 12, each rotor 14 extending along a respective rotation axis C parallel to the extrusion axis A and being rotatable about said rotation axis C. The extruder 6 comprise for example one single rotor 14 or two parallel rotors 14.

[0070] The extruder 6 optionally comprises a die 16 arranged at an end of the barrel 10 to define the outlet 6B of the extruder 6 such that upon operation, the paste P fed to the extruder 6 is extruded through the die 16.

[0071] In other examples, the die 16 is omitted, and the outlet 6B of the extruder 6 is for example defined by an end of the barrel 10.

[0072] When the die 16 is omitted, the paste exiting the outlet 6B of the extruder 6 is for example portioned into paste portion PP such as chunks without precisely defined shapes. The pressure in the extruder 6 can be advantageously reduced.

[0073] The extruder 6 comprises an extrusion driving device 18 for driving each rotor 14 in rotation as illustrated by arrow R1. The extrusion driving device 18 comprises for example one or more actuators, in particular one or more electrical motors.

[0074] The one or more rotors 14 are configured for conveying the paste P from the inlet 6A to the outlet 6B of the extruder 6 upon rotation of the rotor(s) 14 about the rotation axis C with mechanically processing the paste. The extruder 6 is in particular configured for kneading the paste P in the extruder 6. In particular, the one or more rotors 14 are configured for kneading the paste P in the extruder 6 upon rotation of the rotor(s) 14.

[0075] The extruder 6 comprises for example one or more kneading zones 20 and preferably one or more conveying zones 22 distributed along the extruder 6 between the extruder inlet 6A and the extruder outlet 6B.

[0076] A “zone” designates here a section of the extruder, i.e. a portion of length of the extruder 6 located between the extruder inlet 6A and the extruder outlet 6B.

[0077] Each kneading zone 20 is distinct from each conveying zone 22. The one or more kneading zones 20 and the one or more conveying zones 22 are located in respective sections or length portions of the extruder 6 between the extruder inlet 6A and the extruder outlet 6B.

[0078] Each kneading zone 20 is configured for kneading the paste P.

[0079] “Kneading” of the paste P refers here to compressing the paste P perpendicular to the extrusion axis A.

[0080] In particular, in each kneading zone 20, the one or more rotors 14 are configured for kneading the paste P upon rotation of the rotor(s) 14.

[0081] To this end, in each kneading zone 20, each rotor 14 is for example provided with one or several kneading elements 24. Each kneading element 24 is driven in rotation about the rotation axis C upon rotation of the rotor 14 on which the kneading element 24 is provided.

[0082] As illustrated on Figure 2, each kneading element 24 has for example a non-circular contour with first regions 24A remote from the central axis and second regions 24B closer to the central axis, the first regions 24A for compressing or crushing the paste P radially against an inner surface of the chamber 12 upon rotation of the rotor 14. The distance of each first region 24A to the central axis (i.e. radial distance) is greater than the distance of each second region 24B to the central axis. Each first region 24A forms on the circumference of the kneading element 24 a protrusion protruding radially with respect to each second region 24B. For example, the radial distance of the first region 24A is about 1.5 to 5 times the radial distance of the second region 24B. Two opposed first regions 24A may have the same radial distance (as illustrated) or different radial distances. For example, a first region 24A may be longer than its opposed first region 24A.

[0083] In order to ensure an effective compression, the radial distance of the first regions 24A and / or of the second regions 24B is preferably substantially constant along at least a major dimension of the kneading element in the longitudinal direction. The first regions 24A alternate for example circumferentially with the second regions 24B, i.e. on the circumference of the kneading element 24.

[0084] Each rotor is for example provided in each kneading zone 20 with two or more kneading elements 24 provided successively along the extruder with being offset angularly such that the first regions 24A of each preceding kneading element 24 are offset angularly with respect to the first regions 24A of the following kneading element 24.

[0085] Each conveying zone 22 is configured for conveying the paste P along the extrusion axis A towards the extruder outlet 6B, i.e. for pushing the paste along the extrusion axis A.

[0086] In particular, in each conveying zone 22, the one or more rotors 14 are configured for conveying the paste P towards the extruder outlet 6B upon rotation of the rotor(s) 14.

[0087] To this end, in each conveying zone 22, each rotor 14 is for example provided with a screw element 26 such upon rotation of the rotor 14 the screw element 26 forces the paste P towards the outlet 6B of the extruder 6. When two parallel rotors 14 are provided, in each conveying zone 22, threads of the screws element 26 of the rotor 14 are preferably intermeshed.

[0088] The extruder comprises advantageously two or more kneading zones 20 distributed along the extruder 6, preferably three or more kneading zones 20 distributed along the extruder, in particular three kneading zones 20.

[0089] A plurality of kneading zones 20 allows kneading the paste P several times and / or with different kneading parameters. Kneading parameters include for example a maximum pressure of the paste inside the kneading zone. The two or more kneading zones 20 are preferably spaced along the extruder 6. In other words, each preceding kneading zone 20 is separated from the next kneading zone 20 from a non-zero distance along the extruder 6.

[0090] The one or more conveying zones 22 comprises for example at least one intermediate conveying zone 22, each intermediate conveying zone 22 being located along the extruder 6 between two kneading zones 20, preferably one intermediate conveying zone between each preceding kneading zone 20 and the next kneading zone 20.

[0091] In particular examples, the extruder 6 comprises an alternation of kneading zones 20 and conveying zones 22 along the extruder 6. In other words, kneading zones 20 and conveying zones 22 alternate along the extruder 6.

[0092] The provision of an intermediate conveying zone 22 between two successive kneading zones 20 (a preceding kneading zone 20 and the next kneading zone 20) allows separating the kneading processing performed on the paste P by the two successive kneading zones 20 with conveying the paste P along the extruder 6 to feed the paste P from the preceding kneading zone 20 to the next kneading zone 20 with appropriate feeding parameters. Feeding parameters comprises for example the pressure of the paste.

[0093] Preferably, the one or more conveying zones 22 include an inlet conveying zone 22 located along the extruder between the extruder inlet 6A and the one or more kneading zones 20 of the extruder 6, in particular between the extruder inlet 6A and the first kneading zone 20 of the extruder 6. This ensures that the paste P is pushed from the extruder inlet 6A towards the one or more kneading zones 20. The inlet conveying zone 22 is adjacent the extruder inlet 6A and is in particular the most upstream zone of the extruder 6.

[0094] Preferably, the one or more conveying zones 22 include an outlet conveying zone 22 located along the extruder between the one or more kneading zones 20 and the extruder outlet 6B provided with die 16, in particular between the last kneading zone 20 of the extruder 6 and the extruder outlet 6B. This ensures that the paste P is appropriately pushed through the outlet, e.g. die 16. The outlet conveying zone 22 is adjacent the extruder outlet 6B and is in particular the most downstream zone of the extruder 6.

[0095] Upon operation, the one or more rotors 14 are driven in rotation about their respective axes by the extruder driving device 18 and push the paste P axially in the chamber 12 with mechanically processing the paste P, in particular with kneading the paste P in each kneading zone 20 while conveying the paste P from the extruder inlet 6A to the extruder outlet 6B thanks to each conveying zone 22.

[0096] The installation 2 comprises a lamination unit or calendaring unit 32 configured for laminating the paste P into a laminated sheet S.

[0097] The calendaring unit 32 comprises a plurality of successive calendaring stations 34 arranged to process the paste P successively, in particular with laminating the paste P.

[0098] Each calendaring station 34 defines a lamination nip or lamination gap 36 for the passage of the paste P, the lamination gap 36 having a height defining a clearance of the calendaring station 34, the clearances of the calendaring stations 34 decreasing from on calendaring station 34 to the next in the conveying direction of the paste. This allows progressively laminating the paste P to a defined thickness at the exit of the calendaring unit 32.

[0099] In some examples, one or more calendaring stations 34 each comprise a pair of rollers 38 defining between them the lamination gap 36 with a determined height defining the clearance of the calendaring station 34.

[0100] In some examples, the calendaring unit 32 comprises one or more calendaring station 34 each comprising a single roller 36 defining the lamination gap 36. The calendaring unit 30 comprises for example a conveyor (not shown) for conveying the paste P each calendaring station 34 with one single roller 36 defining the lamination gap 36 with an upper face of the conveyor, the lamination gap 36 having a height defining the clearance of the conveying station 34.

[0101] The calendaring unit 32 comprises for example three or more calendaring stations 34, preferably between three and five calendaring stations 34, in particular four calendaring stations 34.

[0102] The installation 2 optionally comprises a drier 40 configured for drying the laminated sheet LS to a determined water content. The drier 40 is in particular a continuous drier, i.e. a drier configured for operating with the laminated sheet LS running through the drier 40. The drier 40 comprises for example a drier inlet 40A for receiving the laminated sheet LS and a drier outlet 40B for provided the dried laminated sheet S.

[0103] The drier 40 comprises a heating assembly 42 for heating the laminated sheet LS between the drier inlet 40A and the drier outlet 40B.

[0104] The heating assembly 42 comprises for example a plurality of heaters 44 distributed between the drier inlet 40A and the drier outlet 40B. The heaters 44 are advantageously individually controllable such as to define a temperature profile in the drier 40 between the drier inlet 40A and the drier outlet 40B. The heaters 44 comprises for example electrical resistors configured for generating heat by Joule effect when fed with electricity.

[0105] The drier 40 comprises for example a conveyor 46 configured for conveying the laminated sheet S from the first drier inlet 40A to the first drier outlet 40B. The conveyor 46 is for example a band conveyor.

[0106] The installation 2 optionally comprises a fractioning unit 50 configured for fractioning the paste P at the outlet 6B of the extruder 6 (in particular the end of the barrel 10 or the die 16 when such die 16 is provided) such as to form paste portions PP to be processed by the calendaring unit 30.

[0107] The fractioning unit 50 is for example positioned at the outlet 6B of the extruder 6, e.g. flush with the outlet 6B of the extruder 6 (in particular the end of the barrel 10 or the die 16 when such die 16 is provided). Hence, the extruder 6 may form the paste into a continuous defined section (e.g., rectangular, oval or cylindrical) which is cut by the fractioning unit 50 into past portions PP.

[0108] The fractioning unit 50 comprises for example a cutter 52 movable to cut the paste P at the exit of the die 16. The cutter 52 is for example movable in rotation as illustrated by arrow R2 on Figure 1. The fractioning unit 50 comprises for example a fractioning driving device 54 for driving the cutter 52. The fractioning driving device 54 comprises for example one or more actuators, in particular one or more electrical motors.

[0109] The fractioning unit 50, in particular when combined with a die 16 defining the outlet 6B of the extruder 6, allows for example extruding the paste P into paste portions PP of defined shapes such as slabs and / or pellets. A method of producing an aerosol generating sheet LS that can be implemented with the installation 2 will now be described with reference to Figures 1 and 2.

[0110] The method of producing uses a paste P containing solid plant material PM mixed with water, aerosol former AF and binder B.

[0111] In some examples, the solid plant material PM comprises ground leaf tobacco.

[0112] In some examples, leaf tobacco is ground to particles with a D90 size comprised between 80 pm and 1500 pm before mixing to form the paste P. By definition of the D90 size, 90% of the particles have a size smaller than the D90 size. In other words, 90% of the particles have a size smaller that the D90 size. The particle size is determined by a method carried out with a Malvern MS3000 instrument with dry dispersion unit Aero dry S. The air pressure line is nominally set to 6 bar and air flow of at least 90 l / min.

[0113] In some examples, the binder B comprises cellulose derivative, cellulose ethers, cellulose ester, plant-derived polysaccharide, algae-derived polysaccharide, microorganism-derived polysaccharide, crustacea-derived polysaccharide, starch, protein, polyphosphoric acid, sodium polyacrylate, polyvinylpyrrolidone and combinations thereof.

[0114] In some examples, the binder B comprises methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxymethyl ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, benzyl cellulose, trityl cellulose cyanoethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, cellulose ester(s), guar gum, tara gum, locus beangum, tamarind seed gum, pectin, gum arabic, gum tragacanth, gum karaya, gum ghatti, arabinogalactan, flaxseed gum, cassia gum, psyllium seed gum, artemisia seed gum, carrageenan, agar, alginic acid, propylene glycol alginate, furcellaran, Gloiopelfis furcata extract, xanthan gum, gellan gum, curdlan pullulan, Agrobacterium succinoglycan, welan gum, Macrophomopsis gum, rhamsan gum, chitin, chitosan, glucosamine, starch glycolate, pregelatinized starch, dextrin, wheat gluten, rye gluten and combinations thereof.

[0115] In some examples, the aerosol former comprises: polyhydric alcohols, such as triethylene glycol, 1 ,3-butanediol and glycerine; ester of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic ester of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols such as triethylene glycol 1 ,3-butanediol and most preferred, glycerine, propylene glycol and combinations thereof. Most preferred is a combination of glycerine and propylene glycol.

[0116] The method of producing comprises for example a step E1 of obtaining the paste P by mixing the solid plant material PM with water W, the aerosol former AF and the binder B. When using the installation 2, the mixing is performed in the mixing unit 4.

[0117] The method of producing comprises a step E2 of mechanically processing the paste P, in particular kneading the paste P and extruding the paste P through a die 16. When using the installation 2, the mechanical processing is performed in the in extruder 6.

[0118] Optionally, the method of producing comprises a step E3 of fractioning the paste P into past portions PP. When using the installation 2, the fractioning is for example performed at the exit of the die 16. Paste portions PP may be more suitable for processing the paste P, in particular for introducing the paste P in the calendaring unit 32.

[0119] The method of producing comprises a step E4 of laminating the paste P to form a laminated sheet S of defined thickness. When using the installation 2, the step is performed respectively in the calendaring unit 32.

[0120] In particular, the paste P is for example laminated with passing via the successive calendaring stations 34 of the calendaring unit 32, the calendaring stations 34 being of decreasing clearances to progressively reduce the thickness of the paste P and obtained a laminated sheet S with the defined thickness.

[0121] The method of producing optionally comprises drying the laminated sheet S, for example in a drier 40 of the installation 2.

[0122] In some examples, the initial water content of the paste P is less than 50 wt. %. The initial water content of the paste P is the water content of the paste before extrusion of the paste P.

[0123] In some examples, the final water content of the laminated sheet is less than 16 wt. % and / or more than 5 wt. %. The final water content of the laminated sheet is the water content of the laminated sheet after laminating the sheet or, when applicable, after drying the laminated sheet.

[0124] The water content of the paste P and the laminated sheet LS are preferably determined using the Karl Fischer method of the standard ISO 6488:2021.

[0125] In some examples, the laminated sheet is laminated to a defined thickness comprised between 80 pm and 400 pm.

[0126] In some examples, the tensile strength of the laminated sheet LS is more than 2.5 N / mm2, preferably more than 3.0 N / mm2, more preferably more than 3.5 N / mm2. In some examples, the tensile strength of the laminated sheet is around 3.7 N / mm2.

[0127] The tensile strength of the laminated sheet LS is preferably determined using a Zwicki 1 KN tensile strength measurement device, with a measurement sample having a length of 180mm and a width of 50 mm, with performing the measurement with a pre-force of 1 N / m at 10mm / min speed, a test speed of 20 mm / min with drag force cut-off threshold of 50% of the maximally allowed force of the measurement device (Fmax) and a start of E- modulus determination of 0.05% of reference E-modulus defined in the measurement device’s machine parameters.

[0128] In some examples, the paste contains fibres having an average length comprised between 400 pm and 2500 pm, preferably between 600 pm and 1500 pm, more preferably between 800 pm and 1200 pm.

[0129] The average length of the fibres is preferably determined using a Morfi Neo fiber optical analyzer marketed by Techpap on samples of 30 mg dispersed in 1 L of water and mixed during 20 seconds.

[0130] Providing fibers with an appropriate average length makes the manufacturing easy will provide the appropriate tensile strength to the laminated sheet.

[0131] In some examples, the solid plant material comprises ground leaf tobacco.

[0132] In some examples, the long fibres comprise primarily non-tobacco fibres and / or cellulose fibres. Aerosol generating sheets having a thickness of 250 m were with produced with using fibres having an average fiber length of 800 pm and tobacco powder with a particle size (D90) of 300 pm.

[0133] One aerosol generating sheet was produced with kneading the paste in the extruder as per the invention and another aerosol generating sheet was produced without kneading the paste in the extruder as a comparative example.

[0134] A tensile strength test was performed on both sheets using the Zwicki 1 KN tensile strength measurement device as indicated above.

[0135] The tensile strength measured for the aerosol generating sheet of the comparative example (without kneading) was 2.1 N / mm2 whereas the tensile strength measured for the aerosol generating sheet of the comparative example (with kneading) was 3.7 N / mm2.

[0136] A tensile strength of 3.7 N / mm2 is better than a tensile strength of 2.1 N / mm2 because it makes the material more resistant to strain and degradation.

[0137] With the method of producing of the invention, it is possible to integrate long fibers in the paste with avoiding the fiber spot issue. The integration of long fibers eventually increases the mechanical properties of the laminated sheet, thereby causing fewer disruption of the laminated sheet during further processing, e.g. for manufacturing an aerosol generating substrate for a consumable article for use in an aerosol generating device.

[0138] The initial water content of less than 50 wt.% allows an appropriate mechanical processing in the extruder in combination with the paste P containing long fibres having an average length above 400 pm, in particular an average length in the preferred average length ranges as indicated above and / or in particular when the solid plant material comprises ground leaf tobacco and / or the long fibres comprise primarily non-tobacco fibres and / or cellulose fibres.

[0139] Additional kneading of paste also ensures better integration of binder gel into the paste. This results in more homogenous final material and better binder and aerosol former distribution besides the advantage of good long-fibre-integration. This leads to better tensile strength of the final material and stabilizes aerosol former delivery.

[0140] A relatively high tensile strength prevent the laminated sheet from tearing apart during the subsequent steps of manufacturing and thus prevents undesired stops of the production. It also prevents disintegration of material during secondary production (i.e. tobacco stick making)

[0141] The aerosol generating substrate may for example be used to manufacture consumable articles to be used in aerosol generating device in particular electrically in heat- not-burn devices. Examples of such articles are described in EP3881699.

Claims

CLAIMS1. A method of producing an aerosol generating sheet wherein the solid plant material is mixed with water, aerosol former and a binder to form a paste, wherein:- the paste contains long fibres having an average length above 400 pm,- the paste has a water content of less than 50 wt.%, and- the paste is extruded in an extruder and- the paste is kneaded in one or more kneading zones of the extruder.

2. Method of producing according to claim 1 , wherein the extruder comprises one or more conveying zones configured for conveying the paste in the extruder, each conveying zone being distinct from each kneading zone.

3. Method of producing according to claim 2, wherein the extruder comprises a conveying zone located along the extruder between an inlet of the extruder and a kneading zone of the extruder.

4. Method of producing according to claim 2 or 3, wherein the extruder comprises a conveying zone located along the extruder between a kneading zone of the extruder and an outlet of the extruder.

5. Method of producing according to anyone of the claims 2 - 4, wherein the extruder comprises one or more intermediate conveying zone, each intermediate conveying zone being located along the extruder between two kneading zones.

6. Method of producing according to anyone claims 1 to 6, wherein kneading is performed in at least two kneading zones distributed along the extruder, preferably at least three kneading zones distributed along the extruder.

7. Method of producing according to anyone of claims 1 to 7, wherein the paste is kneaded in one or more kneading zones by kneading elements, each kneading element rotating about an axis aligned or parallel to the extrusion direction.

8. Method of producing according to anyone of the claims 2 - 7, wherein the paste is conveyed in the one or more conveying zones by at least one conveying screw element of the extruder.

9. Method of producing according to anyone of claims 1 to 8, wherein the paste is extruded into paste portions, e.g. slabs and / or pellets and / or chunks, and laminated in a calendaring unit for obtaining a laminated sheet.

10. Method of producing according claim 9, wherein the calendaring unit comprises successive calendaring stations, preferably between three and five calendaring stations, most preferably four calendaring stations, of decreasing laminating gap in the conveying direction.

11. Method of producing according to claims 9 or 10, wherein the laminated sheet is laminated to a defined thickness comprised between 80 pm and 400 pm.

12. Method of producing according to any one of claims 9 - 11 , wherein tensile strength of the laminated sheet is preferably more than 2.5 N / mm2, preferably more than 3.0 N / mm2, more preferably more than 3.5 N / mm2.

13. Method of producing according to anyone of claims 1 to 12, wherein the paste contains fibres having an average length comprised between 400 pm and 2500 pm, preferably between 600 pm and 1500 pm, more preferably between 800 pm and 1200 pm.

14. Method of producing according to anyone of claims 1 to 13, wherein the solid plant material comprises ground leaf tobacco.

15. Method of producing according to claim 14, wherein leaf tobacco is ground to a particle size (D90) comprised between 80 pm and 1500 pm before mixing to form the paste.

16. Method of producing according to anyone of claims 1 to 15, wherein the long fibres comprise primarily non-tobacco fibres and / or cellulose fibres.

17. Method of producing according to anyone of claims 1 to 16, wherein the binder comprises: cellulose derivative, cellulose ethers cellulose ester, plant-derived polysaccharide, algae-derived polysaccharide, microorganism-derived polysaccharide,crustacea-derived polysaccharide, starch, protein, polyphosphoric acid, sodium polyacrylate, polyvinylpyrrolidone and combinations thereof.

18. Method according to claims 17, wherein the binder comprises: methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxymethyl ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, benzyl cellulose, trityl cellulose cyanoethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, cellulose ester(s), guar gum, tara gum, locus bean gum, tamarind seed gum, pectin, gum arabic, gum tragacanth, gum karaya, gum ghatti, arabinogalactan, flaxseed gum, cassia gum, psyllium seed gum, artemisia seed gum, carrageenan, agar, alginic acid, propylene glycol alginate, furcellaran, Gloiopelfis furcata extract, xanthan gum, gellan gum, curdlan pullulan, Agrobacterium succinoglycan, welan gum, Macrophomopsis gum, rhamsan gum, chitin, chitosan, glucosamine, starch glycolate, pregelatinized starch, dextrin, wheat gluten, rye gluten and combinations thereof.

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