CN113194757A

CN113194757A - Method and apparatus for producing sheets of material containing alkaloids

Info

Publication number: CN113194757A
Application number: CN201980083512.XA
Authority: CN
Inventors: M·戴尔伯莱洛
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2018-12-18
Filing date: 2019-12-18
Publication date: 2021-07-30
Anticipated expiration: 2039-12-18
Also published as: EP3897226B1; CN113194757B; US20220079209A1; JP7436485B2; PL3897226T3; JP2022513279A; WO2020127586A1; ES2935502T3; BR112021011185A2; KR20210102260A; HUE060800T2; EP3897226A1

Abstract

The present invention relates to a method for producing a sheet of material containing alkaloids, the method comprising: -mixing the material containing alkaloids with water (6) to form a slurry (11); -forming a sheet (10) from the slurry (11); -compressing the sheet (10) between a first roller (307) and a second roller (308), the rollers (307, 308) forming a gap (311) therebetween, the sheet (10) being inserted into the gap to form a compressed sheet (10) having a desired thickness (t); -changing the diameter (17) of the first roller (307) in order to change the desired thickness (t) of the compressed sheet (10). The invention also relates to an apparatus for producing a sheet (10) of material containing alkaloids.

Description

Method and apparatus for producing sheets of material containing alkaloids

Technical Field

The present invention relates to a casting apparatus and method for producing a cast web of alkaloid containing material.

Background

In particular, the alkaloid containing material is a homogenized tobacco material, which is preferably used in aerosol generating articles, such as cigarettes or tobacco containing "heat non-combustible" type products.

Homogenized tobacco material is also used today when manufacturing tobacco products other than tobacco leaves. Such homogenized tobacco material is typically manufactured from tobacco plant parts, such as tobacco stems or tobacco dust, which are not well suited for the production of cut filler. Typically, tobacco dust is generated as a by-product in the processing of tobacco leaves during manufacture.

The most commonly used forms of homogenized tobacco material are reconstituted tobacco sheet and cast lamina (TCL is an acronym for cast lamina of tobacco). The process to form the homogenized tobacco material sheet typically comprises the step of mixing tobacco dust with a binder to form a tobacco slurry. The pulp is then used to produce a tobacco web, for example by casting a viscous pulp onto a moving metal belt to produce a so-called cast leaf. Alternatively, a slurry having a low viscosity and a high moisture content can be used to produce reconstituted tobacco in a process like papermaking. After preparation, the homogenized tobacco web may be cut into whole leaf tobacco in a similar manner to produce tobacco cut filler suitable for cigarettes and other smoking articles. A process for manufacturing such homogenized tobacco is disclosed, for example, in european patent EP 0565360.

In "heated non-burning" aerosol-generating articles, the aerosol-forming substrate is heated to a relatively low temperature to form an aerosol, but to prevent combustion of the tobacco material. In addition, the tobacco present in the homogenized tobacco material is typically only tobacco, or a substantial portion of the tobacco present in homogenized tobacco material comprising such "heated non-combustible" aerosol-generating articles. This means that the aerosol composition generated by such a "heated non-burning" aerosol-generating article is substantially based on homogenized tobacco material only. It is therefore important to have good control over the composition of the homogenized tobacco material to control, for example, the taste of the aerosol.

Due to variations in the physical properties of the slurry, such as the consistency, viscosity, fiber size, particle size, humidity or age of the slurry, standard casting methods and equipment can result in undesirable variations in the application of the slurry onto a support during casting of a web of homogenized tobacco. Non-optimal casting methods and equipment may result in non-uniformities and defects in the cast web of homogenized tobacco.

An important parameter of the cast sheet is its thickness, which is preferably as uniform as possible, so that the smoking experience of the user can be substantially the same for any end product obtained using the embedded cast sheet. Variations in thickness, even minimal variations, can result in products that need to be discarded, thereby increasing cost and production time.

In the known process, the thickness of the web is determined by a casting blade that casts the web onto a conveyor belt, and the distance between the blade and the conveyor belt substantially determines the thickness of the web. Any defects in the blades, belts, or their alignment may result in uneven sheet material.

Furthermore, changes in the desired thickness of the cast sheet require careful and slow realignment and movement of the casting blade, which takes time and often causes the machine to stop before the desired new thickness is reached.

Therefore, there is a need for a method and apparatus to obtain a cast sheet of material having a substantially uniform thickness containing alkaloids, which also allows for relatively rapid thickness variations.

Disclosure of Invention

The present invention relates to a method for producing a sheet of material containing alkaloids, the method comprising: mixing an alkaloid containing material with water to form a slurry; forming a sheet from the slurry; compressing a sheet between a first roller and a second roller, the first roller and the second roller forming a gap therebetween, the sheet being inserted into the gap to form a compressed sheet having a desired thickness; and varying the diameter of the first roller to vary the desired thickness of the compressed sheet.

In the method of the invention, the thickness of the sheet is controlled by the compression step between the rollers. Once the sheet is formed, for example by casting or by extrusion, the sheet is compressed between a first pair of rollers to obtain the desired thickness of the sheet. In case it is desired to change the thickness of the sheet, or in case the resulting measured thickness is not the desired thickness, the apparatus can be quickly adjusted to the new desired thickness changing the diameter of the first roller, so that the compression experienced by the sheet is changed. The diameter of the two rolls can also be varied. The process is relatively simple, but accurate control of the thickness is obtained, which also allows for on-line variation.

As used herein, the term "sheet" means a layered element having a width and length that is substantially greater than its thickness. The width of the sheet is preferably greater than about 10 mm, more preferably greater than about 20 mm or about 30 mm. A continuous "sheet" is referred to herein as a "web". Even more preferably, the width of the sheet of alkaloid containing material is between about 60 millimeters and about 2500 millimeters. As used herein, the term "casting blade" means a longitudinally shaped element, which may have a substantially constant cross-section along a major portion of its longitudinal extension. It shows at least one edge intended to be in contact with a paste-like, viscous or liquid-like substance (e.g. pulp) that will be affected by said edge. The edge may have a sharp and knife-like edge. Alternatively, it may have rectangular or rounded edges.

As used herein, the term "movable support" means any device comprising a surface that is movable in at least one longitudinal direction. The movable support may form a closed loop, providing uninterrupted transport in one direction. The movable support may comprise a conveyor belt. The movable support may be substantially flat and may show a structured or unstructured surface. The movable supports may have no openings in their surfaces or may comprise orifices, preferably of a size such that they are impermeable to the slurry deposited thereon. The movable support may comprise a sheet-like movable and bendable strap. The belt may be made of a metallic material, including but not limited to steel, copper, iron alloys, and copper alloys, or a rubber material. The belt may be made of a high temperature resistant material so that it can be heated to accelerate the drying process of the slurry.

As used herein, the term "slurry" means a liquid, viscous or paste-like material, which may comprise an emulsion of different liquid, viscous or paste-like materials, and may contain a certain amount of solid particles, provided that the slurry still exhibits liquid, viscous or paste-like behavior.

An "alkaloid containing material" is a material that contains one or more alkaloids. The alkaloid may comprise nicotine. Nicotine may be present in, for example, tobacco.

Alkaloids are a group of naturally occurring compounds that contain primarily basic nitrogen atoms. This group also includes some related compounds that are neutral or even weakly acidic. Some synthetic compounds with similar structures are also known as alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur, and, more rarely, other elements such as chlorine, bromine and phosphorus.

Alkaloids are produced by a variety of organisms including bacteria, fungi, plants, and animals. They can be purified from crude extracts of these organisms by acid-base extraction. Caffeine, nicotine, theobromine, atropine, tubocurarine are examples of alkaloids.

As used herein, the term "homogenized tobacco material" refers to a material formed by agglomerating particulate tobacco, which contains the alkaloid nicotine. Thus, the alkaloid containing material may be a homogenized tobacco material.

The most commonly used forms of homogenized tobacco material are reconstituted tobacco sheets and cast leaves (cast leaf). The process to form the homogenized tobacco material sheet typically comprises the step of mixing tobacco dust with a binder to form a slurry. The slurry is then used to produce a tobacco web. For example, so-called casting vanes are created by casting a viscous slurry onto a moving metal belt. Alternatively, a slurry having a low viscosity and a high moisture content can be used to produce reconstituted tobacco in a process like papermaking.

In the method of the present invention, a slurry is formed. The slurry comprises an alkaloid containing material and water. It may also preferably contain a binder and an aerosol former. In addition to those contained in the alkaloid containing material, it may also include cellulose fibers.

The slurry may include a variety of additional different components or ingredients. These components may affect the properties of the cast web of alkaloid containing material. The first component is an alkaloid containing material, for example in powder form. This material may be, for example, a tobacco powder blend, which preferably contains a majority of the tobacco present in the slurry. The tobacco powder blend is the source of the majority of the tobacco in the homogenized tobacco material and thus imparts a taste to the final product, for example to an aerosol generated by heating the homogenized tobacco material. Cellulose pulp containing cellulose fibres is preferably added to the pulp, acting as a reinforcing agent, in order to increase the tensile strength of the web of alkaloid material.

It is also preferred to add a binder in order to enhance the tensile properties of the homogenized sheet. An aerosol former may be added to facilitate aerosol formation. In addition, water may be added to the slurry in order to achieve a particular viscosity and humidity that is optimal for casting a web of alkaloid containing material.

The binder may be added to the slurry in an amount between about 1% and about 5% by dry weight of the slurry. More preferably, it is between about 2% and about 4%. The binder used in the slurry may be any of the gums or pectins described herein. The binder may ensure that the powder of alkaloid containing material remains substantially dispersed throughout the homogenized web. Although any binder may be used, preferred binders are natural pectins (such as fruit, citrus or tobacco pectins), guars (such as hydroxyethyl guar and hydroxypropyl guar), locust bean gums (such as hydroxyethyl and hydroxypropyl locust bean gums), alginates, starches (such as modified or derivatized starches), celluloses (such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl celluloses), tamarind gum, dextrans, pullulan, konjac flour, xanthan gum and the like. A particularly preferred adhesive for use in the present invention is guar gum.

The incorporation of cellulosic fibers in the slurry, acting as a reinforcing agent, generally increases the tensile strength of the web of material containing the alkaloids. Thus, the addition of cellulose fibers can increase the resiliency of the web of material containing the alkaloid. Cellulosic fibers for inclusion in a slurry for a web of material containing alkaloids are known in the art and include, but are not limited to: softwood fibers, hardwood fibers, jute fibers, flax fibers, tobacco fibers, and combinations thereof. In addition to pulping, the cellulosic fibers may be subjected to suitable processes such as refining, mechanical pulping, chemical pulping, bleaching, kraft pulping, and combinations thereof. The cellulose fibers may include tobacco stem material, stems, or other tobacco plant material. Preferably, the cellulosic fibers (e.g., wood fibers) comprise a low lignin content. Alternatively, fibers, such as vegetable fibers, may be used with the above fibers or in alternatives including hemp and bamboo. The length of the cellulose fibres is advantageously between about 0.2 mm and about 4 mm. Preferably, the cellulose fibers have an average length by weight of between about 1 millimeter and about 3 millimeters. Further, preferably, the amount of cellulose fibers is from about 1% to about 7% by dry weight of the total weight of the slurry (or homogenized tobacco sheet).

The average length of the fibers refers to their true length (whether they are crimped or have entanglement), as measured by MORFI COMPACT, commercialized by Techpap SAS. The average length is the mathematical average of the fiber length measured by MORFI COMCACT over the measurements of N fibers, where N > 5. MORFI COMPACT is a fiber analyzer that measures the length of a fiber from a fiber framework, and thus the actual deployed length thereof. An object is considered a fiber if it is measured between 200 and 10000 microns in length and between 5 and 75 microns in width. Fiber length was measured while adding deionized water to the fibers and using Morfi software.

Suitable aerosol-formers for inclusion in the slurry for the sheet of alkaloid containing material (e.g., homogenized tobacco material) are known in the art and include, but are not limited to: monohydric alcohols, such as menthol; polyhydric alcohols such as triethylene glycol, 1, 3-butanediol, and glycerin; polyol esters, such as glycerol mono-, di-or triacetate; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Examples of preferred aerosol formers are glycerol and propylene glycol.

The slurry may have an aerosol former content of greater than about 5% by dry weight. The slurry may have an aerosol former content of between 5% and 30% by dry weight. More preferably, the aerosol former comprises between about 10% and about 25% of the dry weight of the slurry. More preferably, the aerosol former comprises between about 15% and about 25% of the dry weight of the slurry.

The binder and cellulosic fibers are preferably included in a weight ratio of about 1:7 to about 5: 1. More preferably, the binder and cellulosic fibers are included in a weight ratio of about 1:1 to about 3: 1.

The binder and aerosol former are preferably included in a weight ratio of about 1:30 to about 1: 1. More preferably, the binder and aerosol former are included in a weight ratio of about 1:20 to about 1: 4.

The alkaloid containing material is preferably tobacco. The binder and tobacco particles are preferably included in a weight ratio of about 1:100 to about 1: 10. More preferably, the binder and tobacco particles are included in a weight ratio of about 1:50 to about 1:15, even more preferably about 1:30 to 1: 20.

The aerosol former and tobacco particles are preferably included in a weight ratio of about 1:20 to about 1: 1. More preferably, the aerosol former and tobacco particles are included in a weight ratio of about 1:6 to about 1: 2.

The aerosol former and cellulosic fibers are preferably included in a weight ratio of about 1:1 to about 30: 1. More preferably, the aerosol former and cellulosic fibers are included in a weight ratio of about 5:1 to about 15: 1.

The cellulose fibers and tobacco particles are preferably included in a weight ratio of about 1:100 to about 1: 10. More preferably, the weight ratio of cellulose fibers to tobacco particles is preferably between about 1:50 and about 1: 20.

Further, a sheet is formed from the slurry. To form the sheet, a sheet former is preferably used. To form the sheet, the slurry may be cast, for example, along a casting direction, preferably on a movable support. The slurry may be contained in a casting box having orifices at the bottom and at the casting blade. The casting box is preferably box-shaped.

For casting, as a sheet former, a casting blade may be used. The casting blade is preferably arranged perpendicularly to the casting direction. The web of material may be formed by a casting blade that casts a slurry present in a casting box. For example, the slurry falls from the casting box by gravity and comes into contact with the casting blade. The edge of the casting blade forms a gap with the surface of the movable support, and the slurry passes through an aperture defined by the gap.

The slurry may be extruded to form a sheet. Thus, the sheet former may be an extruder. Thus, the sheet exits the extruder where it is preferably compressed and heated. Also in this case, the slurry is preferably extruded onto a movable support. Any process of forming the sheet can be used with the present invention, i.e., any sheet former apparatus is contemplated.

The direction in which the sheet is extruded or cast defines the direction of conveyance of the sheet. To form a continuous sheet or web of alkaloid containing material, the sheet is preferably moved as it is formed so that it can be continuously formed to produce a web. Preferably, the sheet is moved in the conveying direction by a movable support.

The formed sheet is then compressed between two rollers, which form a first pair of rollers or rollers. The rollers of the first pair are referred to as a first roller and a second roller. The first roller and the second roller form a first gap therebetween, and the sheet is inserted into the first gap and compressed. Preferably, the thickness of the sheet after being compressed by the first pair of rollers is smaller than the thickness the sheet had before being compressed by the first pair of rollers.

Preferably, the first and second rollers have a cylindrical shape and have a first and second axis of rotation. Preferably, the first and second axes of rotation are parallel to each other. Preferably, the first and second axes of rotation are perpendicular to the direction of conveyance of the sheet. Preferably, the first and second axes of rotation are parallel to the width of the sheet.

The moisture content of the substantially immediately formed sheet is preferably relatively high before being compressed by the first pair of rollers. The moisture content of the sheet immediately prior to compression between the first and second rollers of the first pair preferably comprises between about 60% to about 85% of the total weight of the sheet. Preferably, the moisture content of the sheet immediately prior to compression between the first and second rollers is between about 65% to about 80% of the total weight of the sheet. More preferably, it is between about 70% and about 78%. The first pair of rollers is preferably positioned directly in front of a sheet former (e.g., an extruder or casting blade) without any other elements therebetween.

Prior to compressing the sheet by the first pair of rollers, the sheet has an initial thickness, also referred to as a first thickness. The initial thickness is preferably between about 0.2 mm and about 2 mm. More preferably, the initial thickness is between about 0.4 mm and about 1 mm. Even more preferably, the initial thickness is between about 0.5 millimeters and about 0.8 millimeters.

After being compressed by the first pair of rollers, the initial thickness of the sheet is preferably reduced, and the initial thickness of the sheet becomes the second thickness after the first pair of rollers.

In the event that a different second thickness of the sheet is desired, or if the second thickness is not the desired thickness, for example due to a change in parameters of the overall process (e.g., a lower density slurry, or the use of a different slurry composition, etc.), the size of the gap between the first and second rolls is varied. This change is performed by changing the diameter size of the first roller of the first pair. The diameters of both the first and second rollers may also vary.

The diameter variation of the first roller means that the diameter of the first roller is changed by any means so that the gap between the first roller and the second roller can be changed. The first roller remains unchanged, only its diameter changes. In the diameter changing step, the first roller is rotatably fixed to the apparatus. This also allows diameter variation while performing compression of the sheet. Thus, an online variation of the gap between the first and second rollers is possible.

Preferably, the step of varying the diameter of the first roller comprises: the diameter of the first roller is changed while rotating the first roller. Production is not interrupted.

The first roller whose diameter is changed may not be in direct contact with the sheet. The sheet may be compressed between the first roller and the second roller, but another element is inserted between the first roller and the sheet. This further element may be a further roller.

This change can be performed on-line without stopping production, as the change in diameter of the first roll may not require a change in roll or any interruption in production. The diameter change may be performed when compressing the sheet. A decrease or increase in the gap between the two rollers of the first pair results in a decrease or increase, respectively, in the second thickness of the sheet.

According to the method of the invention, a simple and rapid variation of the thickness of the sheet can be obtained without machine stop. Furthermore, the variation may be made in any direction, i.e. as this diameter varies, it is possible to make the sheet thicker or thinner. The variation may also be automatic, the only manual operation being the input of a different second thickness value in the feedback system. The sensor may check the second thickness of the sheet material after the first pair of rollers. The measured second thickness may be compared to a desired thickness. If the measured second thickness does not match the desired thickness, the gap between the rollers is changed by changing the diameter of the first roller. The diameters of the first and second rollers may also vary.

Preferably, varying the diameter of the first roller comprises varying the width of the gap. Preferably, changing the diameter of the first roller means a change in the width of the gap, which may be wider or smaller than it was before the change. In this way, thicker or thinner sheets can be formed.

Preferably, changing the diameter of the first roller comprises inflating or deflating the first roller. "aeration" refers to the process of increasing the size of a roll by filling the fluid inside the roll. The fluid may be pressurized air. The rollers may be formed of a material that allows deformation, for example, with inflation or deflation using a pressurized fluid. The material forming the first roller may be an elastic material. The roller may be "tire-like" such that a change in its diameter may be achieved by increasing or decreasing its internal pressure. In this way, a very effective change of the gap width, in particular a relatively fast change, can be achieved.

Preferably, changing the diameter of the first roller comprises changing the temperature of the first roller. As is known, several materials can change their dimensions with temperature. Generally, the higher the temperature, the more volume the material occupies. Preferably, the material in which the first roller is formed has a high thermal expansion. Preferably, the higher the temperature, the larger the diameter of the first roller becomes.

Preferably, the sheet has a moisture content of between about 60% and about 85% of the total weight of the sheet at the beginning of the step of compressing the sheet. Preferably, the step of compressing the sheet between the first and second rollers is performed when the sheet is "as formed" (e.g. as cast) and thus has a high moisture content. In this way, the thickness of the cast sheet can be better adjusted because the slurry is still compliant and soft, easily compressible.

Preferably, the method comprises the step of varying the diameter of the first roller in accordance with the desired thickness of the alkaloid containing sheet. Preferably, a feedback loop is present in the apparatus of the invention, so that there is a constant comparison between the actual thickness of the sheet and the desired thickness. When a thickness change occurs, the diameter of the roller changes to maintain the desired thickness. For example, the thickness of the sheet after the first pair of rollers may be measured, and if the measured thickness is different from the desired thickness, the diameter of the first roller may be changed. More preferably, the diameter of the first roller may be changed if the measured thickness is outside a predetermined thickness range. The predetermined thickness range may be a range centered on the desired thickness.

Furthermore, if it is desired that the thickness of the sheet material is different from the thickness produced at a given moment, the size of the gap between the first and second rollers can be modified by simply changing the diameter of the first roller in order to obtain the new desired thickness without any machine interruption. Preferably, the method comprises the steps of: drying the sheet during the compression step between the first roller and the second roller. Preferably, the sheet is dry, although the thickness of the sheet is adjusted by compression. Therefore, preferably, the first pair of rollers is included in the dryer. Preferably, drying is achieved by a combination of a heated roll surface in direct contact with the sheet and hot air. The first roller and the second roller define an outer surface. Preferably, one or both of the first or second rolls is heated by a hot fluid, such as steam or steam, so that its outer surface becomes hot. Preferably, the temperature of the surface of the heated roll in contact with the dried sheet and the temperature of the heated air are both between about 40 degrees Celsius and about 250 degrees Celsius.

Preferably, the efficiency of the drying step is also improved by the compression step of the first pair of rollers. Typically, drying is performed by a hot fluid. Compression may squeeze some of the water out of the sheet so overall drying takes less time, or may use a lower temperature hot fluid for drying.

Preferably, the method comprises the steps of: the temperature of the first roller or the second roller is adjusted. The efficiency of drying can be further improved by the heated roller. Alternatively, the rollers may be cooled, for example, the temperature of a pair of rollers near the outlet of the dryer may be reduced. Preferably, the temperature of the rollers used for heating or cooling is between about 10 degrees Celsius and about-250 degrees Celsius.

Preferably, the method comprises the steps of: the sheet compressed by the first roller and the second roller is further compressed between the third roller and the fourth roller. Preferably, according to the invention, after the first compression, a second compression of the second pair of rollers takes place. The second compression is performed by the third roller and the fourth roller, which preferably form a second gap therebetween, into which the sheet is introduced and compressed by the second pair of rollers.

Preferably, the second compression occurs downstream of the first compression in the conveying direction of the sheet.

Preferably, the third and fourth rollers have a cylindrical shape and have a third and fourth axis of rotation. Preferably, the third and fourth axes of rotation are parallel to each other. Preferably, the third and fourth axes of rotation are perpendicular to the direction of movement of the sheet. For example, the third and fourth axes of rotation are parallel to the width of the sheet. Thus, preferably, the first, second, third and fourth axes of rotation are all parallel to each other.

After being compressed by the second pair of rollers, the thickness of the sheet is further reduced from the second thickness to a third thickness. After the second pair of rollers, i.e., after the second compression by the second pair of rollers, the third thickness of the sheet is preferably between about 0.5 millimeters and about 0.05 millimeters. More preferably, the third thickness of the sheet is between about 0.3 millimeters and about 0.1 millimeters. The third thickness is the final desired final thickness of the sheet. Thus, the final thickness of the sheet, i.e. the third thickness, is preferably obtained in a multi-step process. Any number of counter rolls may be used. Thus, a better control of the final thickness is obtained, since the size of the roll can be easily controlled, and further the "small" non-uniformities obtained in the first compression can be corrected in the second compression.

More than two pairs of rollers are contemplated in the process of the present invention. An even more precise control of the final thickness of the sheet can be obtained. Thus, the sheet may have a number of intermediate thicknesses from the first thickness as formed to the third final thickness. Reaching the final thickness in several steps allows very precise control of the uniformity of the sheet itself. In the following, N pairs of rollers with N ≧ 2 are considered. The first pair of rollers is considered to be closest to the sheet former while the second pair of rollers is the last pair of rollers and an additional N-2 pairs of rollers are placed between the first and second pairs of rollers.

Preferably, in the case of N pairs of rollers, the pressure applied to the sheet by the rollers increases from the first to the second pair of rollers (the last pair of rollers in the row) and increases monotonically in the N-2 pairs of rollers positioned therebetween along the direction of movement of the sheet.

Preferably, the step of forming the sheet comprises the step of casting the sheet. Preferably, the step of forming the sheet comprises the step of extruding the sheet. The sheet may be formed by any known method. The present invention is applicable to any forming system or method for forming a sheet from a slurry.

Preferably, the method comprises a step of drying the sheet during the compression step between the first pair of rollers, or during the compression step between the second pair of rollers, or between the compression step between the first pair of rollers and the compression step between the second pair of rollers. Preferably, the sheet is dry, although the thickness of the sheet is adjusted by several steps of compression. Therefore, preferably, N pairs of rollers are included in the dryer. Preferably, drying is achieved by a combination of a heated roll surface in direct contact with the sheet and hot air. The rollers are heated by a heated fluid such as steam or steam. Preferably, the temperature of the surface of the heated roll in contact with the dried sheet and the temperature of the heated air are both between about 40 degrees Celsius and about 250 degrees Celsius. Preferably, in the case of N pairs of rolls, all rolls are included in the dryer. Thus, preferably, the drying step occurs during each of the N compression steps, and also occurs as the sheet moves from one pair of rollers to the next.

Preferably, the efficiency of the drying step is also improved by the compression step against a roller. Typically, drying is performed by a hot fluid. Compression may squeeze some of the water out of the sheet so overall drying takes less time, or may use a lower temperature hot fluid for drying.

Preferably, the method comprises the steps of: inserting a rigid element between the first roller and the sheet; and the step of changing the diameter of the first roller comprises: the pressure exerted by the first roller on the rigid element is varied. The first roller may not directly contact the web. A rigid element, such as a roller and more preferably a roller whose diameter is fixed and unchangeable, can be interposed between the web and the first roller. The first roller changes diameter pushing the rigid member toward or away from the sheet, causing the compression on the sheet to change. A rigid element is preferably interposed between the first roller and the sheet to constantly maintain the locally flat surface in contact with the sheet. The outer surface of the first roller may deform from the cylindrical surface when the first roller is inflated or deflated. Thus, inserting the rigid element ensures that the surface in contact with the sheet is always the same, only the applied pressure varies.

The invention also relates to an apparatus for producing a sheet of material containing alkaloids, comprising: a tank adapted to contain a slurry formed from an alkaloid containing material and water; a sheet forming device for forming a sheet from the slurry; a first roller and a second roller forming a gap therebetween, the sheet being inserted into the gap to compress the sheet; a diameter changing device for changing the diameter of the first roller.

Many of the advantages of the present invention have been previously stated and are not repeated herein. The apparatus of the invention comprises a first pair of rolls, for example comprised in a dryer. Compression of the sheet between the rollers may change the thickness of the sheet. Thus, a change in the diameter of the first roller can change the thickness of the sheet. Changes in the diameter of the two rolls are also conceivable; in this case, each roller comprises a diameter-changing device, or the same diameter-changing device works on both the first roller and the second roller.

Preferably, said diameter variation means comprises a pressurised fluid supply means. Preferably, said rollers are inflatable, like a tyre, so that they comprise an outer deformable shell, and so the pressurized fluid supply means can be used to change its diameter, thereby blowing up the shell.

Preferably, the width of the first or second roller is at least twice the width of the slot. The width of the first or second roller is defined as the dimension of the first or second roller along its axis of rotation. The width of the slot is the dimension of the slot along the same axis of rotation. Preferably, the rotation axis is perpendicular to the conveying direction of the sheet. Due to the fact that a change in the diameter of the roller may slightly change the shape of the roller, in particular its flatness, it is preferred that the width of the roller is "much larger" than the width of the sheet (typically corresponding to or depending on the width of the groove) so that the sheet can be compressed in the flat portion of the roller, which is typically the central portion. It is therefore preferred to have a first or second roller that is much larger than the trough for the slurry, which defines the width of the sheet, making it possible to compress the sheet in the central portion of the first or second roller.

Preferably, the sheet forming apparatus includes a casting device. Preferably, the sheet forming apparatus comprises an extrusion device. Any sheet forming apparatus can be used in the present invention, casting and extrusion being the most useful and optimal for obtaining sheets of alkaloid containing material.

Preferably, the apparatus includes a third roller and a fourth roller forming a second gap therebetween, the sheet being insertable into the second gap, the third roller and the fourth roller being positioned downstream of the first roller and the second roller in a moving direction of the sheet.

Preferably, the second gap is smaller than the first gap. In the case of N pairs of rollers, the width of the first gap of the first pair of rollers closest to the forming device is the largest and the width of the second gap of the second pair of rollers is the smallest. The width of the gap of the remaining N-2 pairs of rollers is between the first gap and the second gap.

Preferably, the first pair of rollers comprises a first roller and a second roller, the second pair of rollers comprises a third roller and a fourth roller, and wherein the diameter of the first roller is greater than the diameter of the third roller. In the case of N pairs of rollers, it is preferable that the diameter of the rollers decreases in the moving direction of the sheet. A better control of the sheet thickness is obtained. Preferably, the reduction of the diameter of the roller in turn determines a reduction of the contact surface between the roller and the sheet, and enables a more accurate thickness regulation and control.

Preferably, the width of the gap between the rollers is reduced, moving the rollers closer to each other.

Preferably, the first pair of rollers includes a first roller and a second roller, the second pair of rollers includes a third roller and a fourth roller, and an outer surface of the third roller has a higher hardness than a surface of the first roller. Hardness is a measure of the resistance to local plastic deformation caused by mechanical indentation or wear. Some materials are harder than others. Depending on the material, the rollers may have different hardnesses. The hardness of the steel rollers is preferably between about 1 to about 50HRC (Rockwell scale), the hardness of the plastic rollers is preferably between about D10 to about D100 (shore durometer), and the hardness of the rubber rollers is preferably between about a10 to about a100 (shore durometer). The rollers may be formed of metal, plastic or rubber. The surface of the roll may be coated with layers of different materials having different hardnesses. Preferably, in the case of N pairs of rollers, the hardness of the pair of rollers increases from the first pair of rollers toward the nth pair of rollers in the moving direction (conveying direction) of the sheet.

Preferably, the apparatus includes a thickness sensor to measure a thickness of the sheet, and the diameter changing device changes the diameter of the first roller or the second roller based on an output signal of the thickness sensor. Preferably, a feedback loop is present to elaborate the signal from the sensor and to change the diameter of the roll accordingly.

Preferably, the apparatus further comprises a movable support driven by the first roller or the second roller of the first pair of rollers. Preferably, there is a movable support to convey the sheet along the conveying direction. Preferably, the belt is driven by one roller of the first pair. Preferably, the movable support terminates after the first pair of rollers. Preferably, in the case of N pairs of rollers, the movable support extends through a given number of rollers in the conveying direction of the sheet. Preferably, after the first or second pair of rolls, the sheet is "solid", so it is self-sustaining, and it can be driven by the motorized pair of rolls through the next roll. Preferably, the movable support terminates between the first pair of rollers and the second pair of rollers.

Preferably, the apparatus comprises a rigid member positioned in the gap between the first roller and the second roller such that the sheet is inserted between the second roller and the rigid member. The gap between the first and second rollers is "large" so that another element, such as an additional roller, can be inserted. The change in diameter of the first roller changes the pressure exerted by the rigid element on the sheet.

Drawings

Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings, in which:

figure 1 shows a flow chart of a method for producing a slurry for homogenizing tobacco material according to the invention;

FIG. 2 shows a block diagram of a variant of the method of FIG. 1;

figure 3 shows a block diagram of a method for producing homogenized tobacco material according to the invention;

FIG. 4 shows an enlarged view of a step in the method of FIG. 1, 2 or 3;

FIG. 5 shows an enlarged view of a step in the method of FIG. 1, 2 or 3;

FIG. 6 shows a schematic diagram of an apparatus for carrying out the method of FIGS. 1 and 2;

FIG. 7 shows a schematic diagram of an apparatus for carrying out the method of FIG. 3; and

fig. 8 shows a schematic front view of a different embodiment of a detail of the device of the invention.

Detailed Description

Referring first to fig. 1, a method according to the invention for producing an alkaloid containing material sheet, in this example a homogenized tobacco sheet, from a slurry is shown. The first step of the method of the present invention is to select the tobacco type and tobacco grade 100 to be used in the tobacco blend used to produce the homogenized tobacco material. Tobacco types and tobacco grades used in the process of the invention are, for example, flue-cured, sun-cured, aromatic and filler tobacco.

According to the following steps of the method of the invention, only the selected tobacco type and tobacco grade intended for the production of homogenized tobacco material are processed.

The method comprises a further step 101 of laying down the selected tobacco. This step may include checking tobacco integrity, such as grade and quantity, which may be verified, for example, by a bar code reader for product tracking and traceability. After collection and curing, the tobacco leaves are assigned a grade that describes, for example, stem location, quality, and color.

In addition, the laying step 101 may also comprise the unpacking or unpacking of the tobacco box, provided that the tobacco is transported to the manufacturing premises where the homogenized tobacco material is produced. The de-boxed tobacco is then preferably fed to a weighing station for weighing it.

Further, if desired, the tobacco placement step 101 may include tearing the bale, as tobacco leaves are typically transported in bales when being boxed and shipped.

The tobacco bales are separated according to the tobacco type. For example, there may be a processing line for each tobacco type. The following steps are performed for each tobacco type, as detailed below. These steps may then be performed in a hierarchy such that only one production line is required. Alternatively, different tobacco types may be processed in separate lines. This may be advantageous when some of the tobacco type processing steps are different. For example, in conventional primary tobacco processes, flue-cured tobacco and sun-cured tobacco are at least partially processed in separate processes, as sun-cured tobacco often receives additional flavoring (casting). However, according to the present invention, preferably, the blended tobacco powder is not flavored prior to forming the homogenized tobacco web.

In addition, the method of the present invention includes a step 102 of coarse grinding the tobacco leaves.

According to a variant of the method according to the invention, after the tobacco laying step 101 and before the tobacco coarse grinding step 102, a further shredding step, not shown in the figures, is carried out. In the shredding step, the tobacco is shredded into strips having an average size between about 1 millimeter and about 100 millimeters.

Preferably, after the shredding step, a step of removing non-tobacco material from the rod is performed (not depicted in fig. 1).

The shredded tobacco is then fed to a coarse grinding step 102. Preferably, the flow rate of tobacco into the grinder to coarsely grind the tobacco rod is controlled and measured.

In the coarse grinding step 102, the tobacco rod is reduced to a particle size of between about 0.25 mm and about 2 mm. At this stage, the tobacco particles still retain their cells substantially intact and the resulting particles do not pose relevant transport problems.

By the size of the particles of the alkaloid containing material is meant the Dv95 size. Each of the above listed values indicates a Dv95 of granularity. "v" in Dv95 indicates that the volume distribution is considered. The use of volume distribution introduces the concept of an equivalent sphere. An equivalent sphere is a sphere that is equal to a real particle in the property being measured. Thus, for the light scattering method, it is a sphere that will produce the same scattering intensity as a real particle. This is essentially a sphere of the same volume with the particles. Further, "95" in Dv95 means a diameter where ninety-five percent of the distribution has a smaller particle size and five percent has a larger particle size. Thus, the particle size is this size according to the volume distribution, wherein 95% of the particles have a diameter (of the corresponding sphere having substantially the same volume of particles) smaller than said value. A particle size of 60 microns means that 95% of the particles have a diameter of less than 60 microns, wherein the diameter is the diameter of a sphere having a volume corresponding to the particle.

Preferably, after the coarse grinding step 102, the tobacco particles are transported, for example by pneumatic transport, to a blending step 103. Alternatively, the blending step 103 may be performed before the coarse grinding step 102, or before the shredding step (if present), or alternatively, between the shredding step and the coarse grinding step 102.

In the blending step 103, all of the coarse ground tobacco particles of the different tobacco types selected for the tobacco blend are blended. The blending step 103 is thus a single step for all selected tobacco types. This means that only a single line is required for all the different tobacco types after the blending step.

In the blending step 103, the mixing of the various tobacco types is preferably performed in particulate form.

After the blending step 103, a fine grinding step 104 is performed to achieve a tobacco powder size of about 0.03 mm to about 0.12 mm. This fine grinding step 104 reduces the tobacco size to a powder size suitable for slurry preparation. After this fine grinding step 104, the tobacco cells are at least partially destroyed and the tobacco powder may become sticky. The powder size is Dv95 size, see above.

The tobacco powder thus obtained can be immediately used to form a tobacco slurry. Alternatively, a further step (not shown) of storing the tobacco powder, for example in a suitable container, may be inserted.

Referring now to fig. 2, the method of the invention for manufacturing a homogenized tobacco web is shown. The tobacco powder from the fine grinding step 104 is used in a subsequent slurry preparation step 105. Before or during the slurry preparation step 105, the process of the present invention comprises two further steps: a pulp preparation step 106 in which the cellulose fibers 5 and water 6 are pulped to uniformly disperse and thin the fibers in the water; and a suspension preparation step 107 in which the aerosol former 7 and the binder 8 are premixed. Preferably, the aerosol former 7 comprises glycerol and the binder 8 comprises guar gum. Advantageously, the suspension preparation step 107 comprises premixing the guar gum and the glycerol without introducing water.

The pulp preparation step 105 preferably includes transferring a pre-mixed solution of aerosol former and binder to a pulp mixing tank and transferring pulp to the pulp mixing tank. In addition, the slurry preparation step includes metering the tobacco powder blend into the slurry mixing tank along with the slurry and guar-glycerol suspension. More preferably, this step further comprises processing the slurry with a high shear mixer to ensure homogeneity and homogeneity of the slurry.

Preferably, the slurry preparation step 105 further comprises the step of adding water, wherein water is added to the slurry to obtain the desired viscosity and humidity.

To form a homogenized tobacco web, the slurry formed according to step 105 is preferably transported to a casting box, where it is mixed and then cast in a casting step 108. Preferably, this casting step 108 includes transporting the slurry to a casting station and casting the slurry into a web on a support. Preferably, the cast web thickness, moisture and density are controlled during casting immediately after casting, and more preferably, slurry measurement devices are additionally used for continuous monitoring and feedback control during the entire process.

The desired thickness of the sheet is preferably selected.

The homogenized cast web is then dried in a drying step 111 comprising drying the cast web uniformly and gently, for example in an endless stainless steel belt. The endless stainless steel conveyor belt may comprise individually controllable zones. Preferably, the drying step comprises monitoring the casting blade temperature of each drying zone to ensure a mild drying profile of each drying zone and heating the support where the homogenized cast web is formed. Preferably, the drying profile is a so-called TLC drying profile.

During the drying step 111, a first compression step 109 takes place. The first compression step occurs while the sheet is on the belt. The compression is effected between a first pair of rollers forming a first gap therebetween, into which the sheet is inserted and compressed. After the first compression, the sheet may be removed from the belt so that the sheet is subsequently freestanding. After the compression step 109, the gap between the rollers may be modified in the event that the resulting sheet thickness is not the desired thickness. Thus, a step of changing the diameter of one or both of the rollers is performed, step 110.

In a preferred embodiment, after the first step 109, the sheet is also subjected to a second compression step in step 110a between two rollers forming a second gap therebetween. Preferably, the second gap is smaller than the first gap. This second compression is preferably carried out while also drying. At the end of the compression step, the desired thickness of the sheet is obtained. Preferably, the second gap can also be varied by varying the diameter of the second pair of rollers. This thickness of the sheet may be further varied as a result of the drying process.

At the end of the web drying step 111, a monitoring step (not shown) is performed to measure the moisture content of the dried web and the number of defects present.

The homogenized tobacco web, which has been dried to a target moisture content, is then preferably wound in a winding step 112, for example to form a single main bobbin. This main bobbin can then be used for the production of smaller bobbins by cutting in a small bobbin forming process. The smaller bobbin may then be used to produce aerosol-generating articles (not shown).

In the case where sheets having different thicknesses are desired in another process, the distance between the rollers used in the first, second, and third compression steps may be changed, that is, the width of the first, second, or third gap may be changed, so as to change the thickness of the sheet after the drying step 111.

The method of producing a slurry for homogenizing tobacco material according to fig. 1 is performed using an apparatus 200 for producing a slurry as schematically depicted in fig. 3. The apparatus 200 includes a tobacco receiving station 201 where different tobacco types are accumulated, unstacked, weighed and tested. Optionally, removal of the tobacco containing cartons is performed in the receiving station 201, provided that the tobacco has been shipped into the cartons. The tobacco receiving station 201 also optionally includes a tobacco bale splitting unit.

In figure 3 only one type of tobacco production line is shown, but the same equipment may be present for each tobacco type used in the homogenized tobacco material web according to the invention, depending on when the blending step is performed. In addition, the tobacco is introduced into a shredder 202 for the shredding step. The shredder 202 may be, for example, a pin shredder. The shredder 202 is preferably used to manipulate bales of all sizes, loosen the tobacco rod, and shred the tobacco rod into smaller pieces. The tobacco pieces in each line are transported, for example by means of pneumatic transport 203, to a grinder 204 for the coarse grinding step 102. Preferably, control is performed during transport to discard foreign matter in the tobacco pieces. For example, along the pneumatic transport of shredded tobacco, there may be a chainbelt moving conveyor system, a heavy particle separator and a metal detector, all indicated at 205 in the drawings.

The grinder 204 is used to coarsely grind the tobacco rod to a size of between about 0.25 mm and about 2 mm. The rotor speed of the mill can be controlled and varied based on the tobacco fragment flow rate.

Preferably, a surge bin 206 for uniform mass flow control is located after the coarse grinder 204. Furthermore, for safety reasons, the grinder 204 is preferably equipped with a spark detector and safety shut-off system 207.

The tobacco particles from the grinder 204 are transported to a blender 210, for example, by means of pneumatic transport 208. The blender 210 preferably includes a bin with a suitable valving system. In the blender, all tobacco particles of all different types of tobacco that have been selected for the predetermined blend are introduced. In blender 210, the tobacco particles are blended into a uniform blend. The tobacco particulate blend from blender 210 is transported to a fine grinding station 211.

The fine grinding table 211 is, for example, an impact classifying mill with suitable designed ancillary equipment to produce the correct size fine tobacco powder, i.e., between about 0.03 mm to about 0.12 mm Dv95 sized tobacco powder. After the fine grinding table 211, a pneumatic conveying line 212 is adapted to transport the fine tobacco powder to a buffer powder bin 213 for continuous feeding to a downstream slurry batch mixing tank 214 where the slurry preparation process takes place.

The slurry that has been prepared in step 100-105 of the method of the present invention using the above-described tobacco powder is preferably also cast in a casting station 300 as depicted in fig. 4.

The slurry from the buffer tank (not shown) is transported to the casting table 300 by means of a suitable pump under a fine flow rate control measure. The casting stage 300 preferably includes the following sections. A precision slurry casting box and knife assembly 301 receives slurry from a pump as it is cast onto a support 303 (such as a stainless steel belt) with the desired uniformity and thickness for web formation. A primary dryer 302 having a drying zone or section is provided to dry the cast tobacco web. Preferably, the individual drying zones have steam heating on the bottom surface of the support with hot air and adjustable exhaust control above the support. Within the primary dryer 302, the homogenized tobacco web is dried on a support 303 to a desired final moisture.

Referring now to fig. 5 in greater detail, the movable support 303 comprises a continuous stainless steel conveyor belt having a roller assembly. The precision slurry casting box and knife assembly 301 includes a casting blade 304 and a casting box 305. Preferably, the steel conveyor belt 303 is wound around a pair of

opposed rollers

306, 307. The slurry is cast onto a steel conveyor belt by casting vanes 304 at drum 306, producing a continuous sheet 10 of homogenised tobacco material.

The cast slurry 10 is driven by a steel belt 303 in the casting direction indicated by an arrow 24 in fig. 5, and enters a dryer 302, where the cast slurry is gradually heated and uniformly dried. In fig. 5, the dryer 302 is only partially depicted.

The incoming slurry 11 is introduced into the casting box 305 from an inlet (not shown), particularly a pipe, which is connected to the side wall 14 of the casting box 305 so that the incoming slurry 11 is close to the bottom of the casting box 305.

The slurry 11 from the buffer tank (not shown in the figure) is transferred to the casting box 305 usually by a pump (not shown in the figure). Preferably, the pump includes a flow controller (not visible in the drawing) to control the amount of the slurry 11 introduced into the casting box 305. Advantageously, the pump is designed to ensure that the slurry transfer time is kept to the necessary minimum.

The amount of the slurry 11 in the casting box 305 has a predetermined level, which is preferably kept substantially constant or within a given range. In order to keep the amount of the slurry 11 at substantially the same level, the pump controls the flow of the slurry 11 to the casting box 305.

A casting blade 304 is associated with the casting box 305 to cast the slurry. The casting blade 304 has a dominant dimension that is its longitudinal width. The casting blade defines a first axis positioned along a longitudinal direction thereof.

Between the casting blade 304 and the steel belt 303 there is a gap, the dimensions of which determine (among other things) the initial thickness of the cast web 10 of homogenized tobacco material under casting, which is called initial thickness. This initial thickness is preferably checked, for example by means of a suitable sensor 15 (see fig. 4), which preferably has a feedback loop with the casting blade 304. The gap formed between the casting blade and the steel conveyor belt may be modified on the basis of the signal output by the sensor 15.

The casting blade 304 and the belt 303 face each other, and the belt is partially located below the casting blade 304. The roller 306 conveyor belt 303 preferably rotates in the direction depicted by

arrows

24 and 26.

The casting station 300 also includes a first pair of rollers 310 formed as a first roller and a second roller 308 by a second drum 307. The first roller 307 and the second roller 308 form a first gap 311 therebetween. The casting table 300 further includes a control unit 400 and an actuator 19, which are connected to the first pair of rollers 310 to change a gap 311 formed therebetween.

The belt is also wound around a second drum 307 having a diameter 17. The second roller 307 forms part of a first pair of rollers 310, the first roller 307 being a second roller, a second roller 308 having a diameter 18 being positioned vertically above the first roller 307. The two rollers form a first gap 311 therebetween, which has a changeable thickness. A first pair of rollers 310 is positioned inside the dryer 302. The sheet is inserted into the gap 311 and compressed such that water is removed from the sheet. The thickness of the sheet after the first pair of rollers 310 is referred to as the first thickness and is denoted by t₁And (4) showing.

The gap 311 may change the diameter 17 of the first roller 307 or the

diameters

17, 18 of both the first roller 307 and the second roller 308 by modifying the diameter of the rollers. To modify the

diameter

17 or 18, preferably the sensor 16 detects the thickness of the sheet downstream of the first pair of rollers 310 in the transport direction of the sheet, and if this thickness does not match the desired thickness or if the desired thickness changes, a feedback loop activates the actuator 19 to change the

diameter

17 or 18.

For example, the control unit 400 may receive a signal from the sensor 16 regarding the thickness of the sheet 10 and activate the actuator 19 if the thickness measurement is not a desired value. Alternatively, if a thickness change is desired, the actuator 19 may be activated by the control unit 400.

The diameter variation is shown in figure 7. The roller 307 changes its diameter, for example, it expands the diameter from diameter 17 to diameter 17 'as a first roller 307'. The arrows 20 show the uniform expansion of the surface of the roller, for example caused by the pressurized fluid introduced inside the roller 307.

The first pair of rollers 310 can be the first pair of a series of N pairs of rollers, where N ≧ 2. In fig. 6, N-3 is an example where there is a first pair of rollers 310, a second pair of rollers 312 (the last pair of rollers before the sheet exits the dryer), and a third pair of rollers 313 located between the first and second pairs of rollers. The second pair of rollers is formed by a third roller 314 and a fourth roller 315 forming a second gap 316 therebetween. The third roller 314 has a diameter of 24 and the second roller 315 has a diameter of 25. The thickness of the sheet after the second pair of rollers is called the second thickness and is used t₂And (4) showing. The third pair of rollers interposed between the first pair of rollers 310 and the second pair of rollers 312 is formed by a fifth roller 317 and a sixth roller 318 forming a second gap 319 therebetween. The fifth roller 317 has a diameter 27 and the sixth roller 318 has a diameter 28. The thickness of the sheet after the third pair of rollers is called the third thickness and t₃And (4) showing. Each pair of rollers defines a gap between the rollers forming the pair of rollers. The width of the gap between the pair of rollers decreases monotonically from the first pair of rollers to the second roller. This means that the first gap 311 is wider than the third gap 319, which in turn is wider than the second gap 316. In the same manner, after the first pair of rollers 310, the first thickness of the sheet 10 is from the thickest t₁Reduced to the thinnest t after the second pair of rollers 312₂。

In other words, t₁>t₃>t₂. Preferably, all of the

pair rollers

310, 312, 313All rollers located below the sheet 10 can change their diameter. The diameter 17 of the first roller 317 may vary. The diameter 27 of the fifth roller 317 may vary and the diameter 24 of the third roller 314 may vary.

Preferably, the diameter of the rollers is also reduced from the first pair of rollers 310 to the second pair of rollers 312 (which have the smallest diameter). The third pair of rollers 313 has an intermediate diameter between the first and second pairs of rollers.

The thickness t of the sheet after the second pair of rollers 312 is preferably checked₂For example by means of a suitable sensor 16 positioned downstream of the dryer 302 in the direction of movement of the conveyor belt 303 (see fig. 4 and 5). The feedback loop preferably consists in checking the thickness t₂With a first gap 311, a second gap 316 and a third gap 319 between the first pair of rollers 310, the second pair of rollers 312 and the third pair of rollers 313, respectively. These

gaps

311, 316, 319 can be adjusted based on the signals sent by the sensor 16. The thickness of the sheet can be monitored at different locations. In fig. 8, a different embodiment of the invention is shown. The first pair of rollers 310 includes not only the first roller 307 and the second roller 308, but also an additional rigid roller 500 in contact with the sheet 10. Thus, the sheet 10 contacts the additional rigid roller 500 and the second roller 308. When the first roller 307 changes its diameter, for example by inflating or deflating, the pressure exerted by the rigid roller 500 on the sheet 10 also changes. Rigid roller 500 is positioned within first gap 311.

Downstream of the dryer 302, the dried sheet material may be wound into a bobbin (not shown) to be stored and further used for producing aerosol-generating articles.

Claims

1. A method for producing a sheet of alkaloid containing material, the method comprising:

mixing the alkaloid containing material with water to form a slurry;

o forming a sheet from the slurry;

o compressing the sheet between a first roller and a second roller, the first roller and the second roller forming a gap therebetween, the sheet being inserted into the gap to form a compressed sheet having a desired thickness; and

o varying the diameter of the first roller so as to vary the desired thickness of the compressed sheet.

2. The method of claim 1, wherein changing the diameter of the first roller comprises changing a width of the gap.

3. The method of claim 1 or 2, wherein changing the diameter of the first roller comprises inflating or deflating the first roller.

4. The method of any of the preceding claims, wherein the sheet has a moisture content of between about 60% and about 85% of the total weight of the sheet at the beginning of the step of compressing the sheet.

5. The method according to any of the preceding claims, comprising the steps of:

o varying the diameter of the first or second roller depending on the desired thickness of the sheet containing alkaloid.

6. The method according to any of the preceding claims, comprising the steps of:

o drying the sheet during the compression step between the first and second rollers.

7. The method according to any of the preceding claims, comprising the steps of:

o adjusting the temperature of the first or second roller.

8. The method according to any of the preceding claims, comprising the steps of:

further compressing the sheet compressed by the first and second rollers between a third roller and a fourth roller.

9. The method according to any of the preceding claims, comprising the steps of:

o inserting a rigid element between the first roller and the sheet;

and wherein the step of varying the diameter of the first roller comprises:

o varying the pressure exerted by the first roller on the rigid element.

10. An apparatus for producing a sheet of material containing alkaloids, the apparatus comprising:

a tank adapted to contain a slurry formed from an alkaloid containing material and water;

o a sheet forming device for forming a sheet from the slurry;

o a first roller and a second roller forming a gap therebetween, the sheet being inserted into the gap to compress the sheet;

o diameter changing means for changing the diameter of the first roller.

11. The apparatus of claim 10, wherein the diameter changing device comprises a pressurized fluid supply.

12. The apparatus according to any one of claims 10 or 11, wherein the sheet forming device comprises a casting apparatus or an extrusion apparatus.

13. The apparatus according to any one of claims 10-12, comprising a third roller and a fourth roller forming a second gap therebetween, the sheet being insertable into the second gap, the third and fourth rollers being positioned downstream of the first and second rollers in a direction of movement of the sheet.

14. The apparatus according to any one of claims 10 to 13, comprising a thickness sensor to measure a thickness of the sheet, the diameter changing device changing the diameter of the first roller or the second roller based on an output signal of the thickness sensor.

15. The apparatus of any of claims 10-14, comprising a rigid element positioned in the gap between the first and second rollers such that the sheet is inserted between the second roller and the rigid element.