Method and apparatus for producing sheets of alkaloid-containing material

Abstract

The present invention relates to a method for producing sheets of alkaloid-containing material, the method comprising: mixing a production line alkaloid-containing material with water to form a slurry (105); forming a sheet from the production line slurry (108); compressing the sheet between a first pair of rollers (109) in the production line, wherein the moisture content of the sheet at the start of the compressing step is between about 50 percent and about 80 percent of the total weight of the sheet; and further compressing the sheet compressed by the first pair of rollers between a second pair of rollers (110). The present invention also relates to an apparatus (200) for producing sheets of alkaloid-containing material.

Description

[Technical field]

[0001] The present invention relates to a casting apparatus and method for producing a cast web of alkaloid-containing material. [Background technology]

[0002] In particular, the alkaloid-containing material is a homogenized tobacco material, preferably for use in aerosol-generating articles such as cigarettes, or "heat-not-burn" type tobacco-containing products.

[0003] Today, in addition to tobacco leaves, homogenized tobacco materials are also used in the manufacture of tobacco products. These homogenized tobacco materials are typically produced from parts of the tobacco plant that are less suitable for the production of cut filler (e.g., tobacco stems or tobacco dust). Typically, tobacco dust is produced as a by-product during the handling of tobacco leaves during production.

[0004] The most commonly used forms of homogenized tobacco material are reconstituted tobacco sheets and cast leaves (TCL is an acronym for tobacco cast leaf). The process of forming homogenized tobacco material sheets generally involves mixing tobacco dust with a binder to form a tobacco slurry. The slurry is then used to create a tobacco web, for example by casting the viscous slurry onto a moving metal belt to produce so-called cast leaves. Alternatively, a slurry with a low viscosity and high moisture content can be used to create reconstituted tobacco in a process similar to papermaking. Once the homogenized tobacco web is prepared, it may be cut in a manner similar to uncut intact tobacco leaves to produce tobacco cut filler suitable for cigarettes and other smoking articles. A process for making such homogenized tobacco is disclosed, for example, in European Patent No. EP0565360.

[0005] In "heat-and-burn" aerosol-generating articles, the aerosol-forming substrate is heated to a relatively low temperature to form an aerosol but prevent the combustion of the tobacco material. Furthermore, the tobacco present in the homogenized tobacco material is typically the only tobacco or comprises the majority of the tobacco present in the homogenized tobacco material of such "heat-and-burn" aerosol-generating articles. This means that the aerosol composition generated by such "heat-and-burn" aerosol-generating articles is substantially based only on the homogenized tobacco material. Thus, it is important to have good control of the composition of the homogenized tobacco material, for example, for control of the taste of the aerosol.

[0006] For example, standard casting methods and casting equipment may result in unintended variations in the application of the slurry on the substrate during casting of the homogenized tobacco web due to changes in the physical properties of the slurry, such as its concentration, viscosity, fiber size, particle size, moisture, or changes over time. Suboptimal casting methods and casting equipment may lead to inconsistencies and defects in the homogenized tobacco cast web.

[0007] An important parameter of the cast sheet is its thickness, which is preferably as uniform as possible so that the smoking experience of a user using any final product resulting from embedding the cast sheet is substantially the same. Variations in thickness (even minimal variations) can result in product having to be discarded, increasing costs and extending production times.

[0008] In known processes, the thickness of the sheet is determined by a casting blade that casts the sheet onto a conveyor belt, and the distance between the blade and the belt substantially determines the thickness of the sheet. Any imperfections in the blade, conveyor belt, or their alignment can result in the production of non-uniform sheets. Summary of the Invention [Problem to be solved by the invention]

[0009] Thus, there is a need for a method and apparatus for obtaining cast sheets of alkaloid-containing material having a substantially uniform thickness. [Means for solving the problem]

[0010] The present invention relates to a method for producing a sheet of an alkaloid-containing material, the method including mixing an alkaloid-containing material with water to form a slurry, forming a sheet from the slurry, compressing the sheet between a first set of rollers, where the moisture content of the sheet at the start of the step of compressing the sheet is comprised between about 50% and about 80 percent of the total weight of the sheet, and further compressing the sheet compressed by the first set of rollers between a second set of rollers.

[0011] The present invention also relates to a method for producing a sheet of an alkaloid-containing material, the method including mixing an alkaloid-containing material with water to form a slurry, forming a sheet from the slurry, compressing the sheet between a first pair of rollers, where the moisture content of the sheet at the start of the step of compressing the sheet is comprised between about 50% and about 80 percent of the total weight of the sheet, and further compressing the sheet compressed by the first pair of rollers between a second pair of rollers.

[0012] In the method of the present invention, the thickness of the sheet is controlled by a subsequent compression step between rollers. Once the sheet is formed, for example by casting or by extrusion, it is compressed between a first set of rollers and then by a second set of rollers to obtain the desired thickness of the sheet. Although the process is relatively simple, precise control of the thickness is obtained because the final thickness is obtained in at least two steps, not in a "single step". Three or more sets of rollers can be used as well. The control of the thickness of the sheet is improved.

[0013] In this document, "pair" and "set" have the same meaning. A pair of rollers or a set of rollers means two rollers.

[0014] The term "sheet" as used herein means a layered element having a width and length substantially greater than its thickness. The width of the sheet of alkaloid-containing material is preferably greater than about 10 millimeters, more preferably greater than about 20 millimeters or about 30 millimeters. Even more preferably, the width of the sheet of alkaloid-containing material is comprised between about 60 millimeters and about 2500 millimeters. A continuous "sheet" is referred to herein as a "web."

[0015] The term "casting blade" as used herein means a longitudinally shaped element that may have an essentially constant cross section along the majority of its longitudinal extension. It exhibits at least one edge, which is intended to come into contact with a pasty, viscous or liquid-like substance (such as a slurry) that will be affected by said edge. Said edge may have a sharp and knife-like edge. Alternatively, said edge may have a rectangular or rounded edge.

[0016] The term "movable support" as used herein means any means with a surface capable of moving in at least one longitudinal direction. The movable support may form a closed loop to provide uninterrupted transport in one direction. The movable support may include a conveyor belt. The movable support may be essentially flat and may exhibit a structured or unstructured surface. The movable support may have no openings in its surface or may include orifices, preferably of a size such that the slurry deposited thereon cannot penetrate. The movable support may include a sheet-like movable and bendable strip. The strip may be made of a metallic material, including but not limited to steel, copper, iron alloys, and copper alloys, or a rubber material. The strip may be made of a heat-resistant material so that it can be heated to accelerate the drying process of the slurry.

[0017] The term "slurry" as used herein means a liquid-like, viscous, or pasty material that may include an emulsion of different liquid-like, viscous, or pasty materials and may contain a certain amount of solid-state particles (although a slurry still exhibits liquid-like, viscous, or pasty behavior).

[0018] An "alkaloid-containing material" is a material that contains one or more alkaloids. The alkaloids may include nicotine. Nicotine may be found, for example, in tobacco.

[0019] Alkaloids are a group of naturally occurring compounds that contain mostly basic nitrogen atoms. The group also includes some related compounds with neutral properties, and even some related compounds with weakly acidic properties. Some synthetic compounds of similar structure are also called alkaloids. In addition to carbon, hydrogen, and nitrogen, alkaloids may also contain other elements such as oxygen, sulfur, and more rarely chlorine, bromine, and phosphorus.

[0020] Alkaloids are produced by a wide variety of organisms, including bacteria, fungi, plants, and animals. Alkaloids can be purified from crude extracts of these organisms by acid-base extraction. Caffeine, nicotine, theobromine, atropine, and tubocurarine are examples of alkaloids.

[0021] As used herein, the term "homogenized tobacco material" refers to a material formed by agglomerating particulate tobacco that contains the alkaloid nicotine. Thus, an alkaloid-containing material can be a homogenized tobacco material.

[0022] The most commonly used forms of homogenized tobacco material are reconstituted tobacco sheets and cast leaves. The process of forming homogenized tobacco material sheets generally involves mixing tobacco dust with a binder to form a slurry. The slurry is then used to create a tobacco web. For example, the viscous slurry is cast onto a moving metal belt to produce so-called cast leaves. Alternatively, a slurry with a low viscosity and high moisture content can be used to create reconstituted tobacco in a process similar to papermaking.

[0023] The term "aerosol-forming substrate" refers to a substrate capable of releasing volatile compounds that may form an aerosol. Typically, the aerosol-forming substrate releases the volatile compounds upon heating. The aerosol-forming substrate may comprise an alkaloid-containing material that contains a volatile alkaloid flavour compound, which is released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise a homogenised material.

[0024] In the method of the present invention, a slurry is formed. The slurry contains an alkaloid-containing material and water. It may also preferably contain a binder and an aerosol former. It may also contain cellulose fibers in addition to those contained in the alkaloid-containing material.

[0025] The slurry may contain a number of additional different components or ingredients. These components may affect the properties of the cast web of alkaloid-containing material. The first component is the alkaloid-containing material, for example in powder form. This material may be, for example, a tobacco powder blend, which preferably contains the 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 therefore provides flavor to the final product, for example the aerosol produced by heating the homogenized tobacco material. To increase the tensile strength of the alkaloid material web, a cellulose pulp containing cellulose fibers is preferably added to the slurry, which acts as a reinforcing agent.

[0026] The powder of the alkaloid-containing material preferably has a size of about 0.03 millimeters to about 0.12 millimeters. The size of the particles or powder of the alkaloid-containing material refers to the Dv95 size. Each of the values ​​listed above indicates the Dv95 of the particle size. The "v" in Dv95 means that the volume distribution is taken into account. The use of the volume distribution introduces the concept of an equivalent sphere. An equivalent sphere is a sphere that is equivalent to the actual particle in the property we are measuring. It is therefore a sphere that will produce the same scattering intensity as the actual particle in light scattering methods. This is essentially a sphere with the same volume of particles. Furthermore, the "95" in Dv95 refers to the diameter at which 95 percent of the distribution has a smaller particle size and 5 percent has a larger particle size. The particle size is therefore that size by volume distribution at which 95 percent of the particles have a diameter smaller than the stated value (the diameter of the corresponding sphere having substantially the same volume of the particle). A particle size of 60 micrometers means that 95 percent of the particles have a diameter smaller than 60 micrometers, the diameter being the diameter of a sphere having a corresponding volume smaller than the particle.

[0027] The Dv95 size of particles is measured using a Horiba LA950 or LA960 particle size distribution analyzer. The HORIBA LA-960 particle size analyzer measures size distribution using laser diffraction. This technique uses first principles to calculate size using light scattered off the particle (edge ​​diffraction) and light transmitted through the particle (secondary scattering refraction). The LA-960 incorporates Mie scattering theory.

[0028] A binder is preferably added to enhance the tensile properties of the homogenized sheet. An aerosol former may be added to the slurry to facilitate the formation of an aerosol. Additionally, water may be added to the slurry to reach a certain viscosity and moisture content that is optimal for casting a web of the alkaloid-containing material.

[0029] The amount of binder added to the slurry may comprise from about 1 percent to about 5 percent by dry weight of the slurry. More preferably, the amount of binder comprises from about 2 percent to about 4 percent. The binder used in the slurry may be any of the gums or pectins described herein. The binder may ensure that the powder of the alkaloid-containing material remains substantially dispersed throughout the homogenized web. While any binder may be employed, preferred binders are natural pectins (such as fruit pectins, citrus pectins, or tobacco pectins), guar gums (such as hydroxyethyl guar, hydroxypropyl guar, etc.), locust bean gums (such as hydroxyethyl locust bean gum, hydroxypropyl locust bean gum, etc.), alginates, starches (such as modified or derivatized starches), celluloses (such as methylcellulose, ethylcellulose, ethylhydroxymethylcellulose, carboxymethylcellulose, etc.), tamarind gum, dextran, pralon, konjac flour, xanthan gum, and the like. A particularly preferred binder for use in the present invention is guar.

[0030] The introduction of cellulose fibers into the slurry typically increases the tensile strength of the web of alkaloid-containing material and acts as a reinforcing agent. Thus, adding cellulose fibers may increase the elasticity of the web of alkaloid-containing material. Cellulosic fibers for inclusion in slurries for webs of alkaloid-containing material are well known in the art, including, but not limited to, softwood fibers, hardwood fibers, jute fibers, flax fibers, tobacco fibers, and combinations thereof. In addition to pulping, the cellulose fibers may be subjected to suitable processing, such as refining, mechanical pulping, chemical pulping, bleaching, sulfate pulping, and combinations thereof. The cellulose fibers may include tobacco stem material, petioles, or other tobacco plant materials. Cellulosic fibers, such as wood fibers, preferably include a low lignin content. Alternatively, fibers such as vegetable fibers may be used in conjunction with or as a replacement for the above fibers, including hemp and bamboo. The length of the cellulose fibers is advantageously about 0.2 millimeters to about 4 millimeters. The average length by weight of the cellulose fibers is preferably about 1 millimeter to about 3 millimeters. Further, the amount of cellulose fibers preferably comprises from about 1 percent to about 7 percent, on a dry weight basis, of the total weight of the slurry (or homogenized tobacco sheet).

[0031] The average length of fibres refers to their actual length (whether they are curled or kinked) as measured by the MORFI COMPACT commercialized by Techpap SAS. The average length is the mathematical average of the fibre lengths measured by the MORFI COMPACT for measurements of N fibres (where N>5). The MORFI COMPACT is a fibre analyzer that measures the fibre length according to the fibre structure and therefore measures the actual generated length of the fibre. A measured object is considered a fibre if its length is comprised between 200 micrometres and 10000 micrometres and its width is comprised between 5 micrometres and 75 micrometres. The fibre length is measured when deionised water is added to the fibre and the Morfi software is used.

[0032] Suitable aerosol formers for inclusion in a slurry for a sheet of alkaloid-containing material (such as homogenized tobacco material) are well 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, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.).

[0033] Examples of preferred aerosol formers are glycerin and propylene glycol.

[0034] The slurry may have an aerosol former content of greater than about 5 percent on a dry weight basis. The slurry may have an aerosol former content of about 5 percent to about 30 percent on a dry weight basis. More preferably, the aerosol former comprises about 10 percent to about 25 percent of the dry weight of the slurry. More preferably, the aerosol former comprises about 15 percent to about 25 percent of the dry weight of the slurry.

[0035] The binder and the cellulose fibers are preferably contained in a weight ratio comprised between about 1:7 and about 5:1, and more preferably in a weight ratio comprised between about 1:1 and about 3:1.

[0036] The binder and the aerosol former are preferably present in a weight ratio of about 1:30 to about 1:1. More preferably, the binder and the aerosol former are present in a weight ratio of about 1:20 to about 1:4.

[0037] The alkaloid-containing material is preferably tobacco. The binder and tobacco particles are preferably present in a weight ratio of about 1:100 to about 1:10. More preferably, the binder and tobacco particles are present in a weight ratio of about 1:50 to about 1:15, and even more preferably, about 1:30 to 1:20.

[0038] The aerosol formers and tobacco particles are preferably included in a weight ratio of about 1:20 to about 1:1. The aerosol formers and tobacco particles are more preferably included in a weight ratio of about 1:6 to about 1:2.

[0039] The aerosol-forming material and the cellulose fibers are preferably included in a weight ratio of about 1:1 to about 30:1. The aerosol-forming material and the cellulose fibers are more preferably included in a weight ratio of about 5:1 to about 15:1.

[0040] The cellulose fibers and tobacco particles are preferably contained in a weight ratio of about 1:100 to about 1:10. The cellulose fibers and tobacco particles are more preferably contained in a weight ratio of about 1:50 to about 1:20.

[0041] Further, a sheet is formed from the slurry. To form a sheet, the slurry can be cast along a casting direction, for example, preferably on a movable support. The slurry can be contained in a casting box having an opening at the bottom and a casting blade. The casting box is preferably box-shaped.

[0042] The casting blade is preferably arranged perpendicular to the casting direction. The web of material may be formed by the casting blade casting the slurry present from a casting box. The slurry falls, for example, by gravity from the casting box and comes into contact with the casting blade. The edge of the casting blade edge actually forms a gap with the surface of the movable support, and the slurry passes through the opening defined by said gap.

[0043] The slurry may be extruded to form a sheet. Thus, the sheet preferably exits an extruder where it is compressed and heated. Also, in this case, the slurry is preferably extruded onto a movable support. Any process for forming a sheet may be used in the present invention, i.e., any sheet forming apparatus is contemplated.

[0044] The direction along which the sheet is extruded or cast also defines the transport direction of the sheet. To form a continuous sheet or web of alkaloid-containing material, the sheet needs to be moved (while it is being formed), so that the sheet can be continuously formed while creating the web. The sheet is preferably moved along the transport direction by a movable support.

[0045] The formed sheet is then compressed between two rollers forming a first set of rollers. The rollers of the first set of rollers are referred to as the first roller and the second roller. The first roller and the second roller form a first gap between them, into which the sheet is inserted and compressed. The thickness of the sheet after being compressed by the first set of rollers is preferably less than the thickness of the sheet before being compressed by the first set of rollers.

[0046] The first roller and the second roller preferably have a cylindrical shape and a first rotation axis and a second rotation axis. The first rotation axis and the second rotation axis are preferably parallel to each other. The first rotation axis and the second rotation axis are preferably perpendicular to the conveying direction of the sheet. For example, the first rotation axis and the second rotation axis are parallel to the width of the sheet.

[0047] Prior to compression by the first set of rollers (hereinafter referred to as the first compression), the moisture content of the substantially freshly formed sheet is relatively high. The moisture content of the sheet immediately prior to compression between the first and second rollers of the first set comprises about 50 percent to about 80 percent of the total weight of the sheet. The moisture content of the sheet prior to compression between the first and second rollers preferably comprises about 50 percent to about 70 percent of the total weight of the sheet, more preferably about 50 percent to about 65 percent, and even more preferably about 50 percent to about 60 percent. The first set of rollers is preferably positioned immediately in front of a sheet forming device such as an extruder or casting blade, without any other elements between them.

[0048] Prior to compression of the sheet by the first set of rollers, the sheet has a first thickness. Preferably, the first thickness is comprised between about 0.2 millimeters and about 2 millimeters. More preferably, the first thickness is comprised between about 0.3 millimeters and about 1.5 millimeters. More preferably, the first thickness is comprised between about 0.4 millimeters and about 1 millimeter. More preferably, the first thickness is comprised between about 0.5 millimeters and about 0.9 millimeters. Even more preferably, the first thickness is comprised between about 0.5 millimeters and about 0.8 millimeters.

[0049] After the first compression by the first set of rollers, the thickness of the sheet is preferably reduced, the thickness of the sheet being reduced to a second thickness that is less than the first thickness.

[0050] Furthermore, after the first compression, a second compression by a second set of rollers is performed according to the invention, the second compression being carried out by a third roller and a fourth roller, which preferably form a second gap between them, in which gap the sheet is introduced and compressed by the second set of rollers.

[0051] The second compression is performed downstream of the first compression in the conveying direction of the sheet.

[0052] The third roller and the fourth roller preferably have a cylindrical shape and a third rotation axis and a fourth rotation axis. The third rotation axis and the fourth rotation axis are preferably parallel to each other. The third rotation axis and the fourth rotation axis are preferably perpendicular to the sheet conveying direction. For example, the third rotation axis and the fourth rotation axis are parallel to the width of the sheet. Therefore, it is preferable that the first rotation axis, the second rotation axis, the third rotation axis, and the fourth rotation axis are all parallel to each other.

[0053] After the second compression by the second set of rollers, the thickness of the sheet is further reduced from the second thickness to a third thickness. After the second set of rollers, i.e., after the second compression by the second set of rollers, the third thickness of the sheet is preferably comprised between about 0.05 millimeters and about 0.5 millimeters. Even more preferably, the third thickness of the sheet is comprised between about 0.07 millimeters and about 0.45 millimeters. Even more preferably, the third thickness of the sheet is comprised between about 0.1 millimeters and about 0.4 millimeters. Even more preferably, the third thickness of the sheet is comprised between about 0.1 millimeters and about 0.3 millimeters. The third thickness is substantially the final desired thickness of the sheet.

[0054] In the method of the present invention, the final thickness of the sheet, which is preferably equal to the third thickness, is obtained in a multi-step process. Thus, better control of the final thickness is obtained, since the roller dimensions can be easily controlled. Moreover, the "small" non-uniformities obtained by the first compression can be corrected by the second compression.

[0055] Furthermore, sheets for which different final thicknesses are desired can be handled using the same method of the present invention by simply adjusting the gap defined by the first set of rollers or the second set of rollers.

[0056] In the method of the invention, three or more sets of rollers can be considered. Even more precise control of the final thickness of the sheet can be obtained. Thus, from the first (initial) thickness to the third (final) thickness, the sheet may have many intermediate thicknesses. Reaching the final thickness in several steps allows a very precise control of the homogeneity of the sheet itself. In the following, N sets of rollers (where N is 2 or more) are considered. The first set of rollers is considered to be closest to the sheet forming device, while the second set of rollers is the last set of rollers, and additional N-2 sets of rollers are placed between the first set of rollers and the second set of rollers.

[0057] Preferably, forming the sheet comprises casting the sheet. Preferably, forming the sheet comprises 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.

[0058] Preferably, the first set of rollers comprises a first roller and a second roller forming a first gap therebetween, and the second set of rollers comprises a third roller and a fourth roller forming a second gap therebetween, and the method comprises a step of varying the width of the first gap or the width of the second gap. The gap defines the distance between the surfaces of the two rollers. This gap or distance is preferably perpendicular. Advantageously, the width of the gap is also preferably adjustable. More preferably, the method comprises varying the diameter of one roller of the first set of rollers or the diameter of one roller of the second set of rollers depending on the desired thickness of the sheet containing the alkaloid. Alternatively or additionally, the width of the gap can be varied, varying the distance between the first roller and the second roller or varying the distance between the third roller and the fourth roller depending on the desired thickness of the sheet containing the alkaloid. The sheet can have different desired thicknesses depending on its specific goal. The final thickness of the sheet is obtained by a subsequent compression step. In the case of N sets of rollers, these can be equal to N, where N is 2 or more. In order to obtain sheets with different final thicknesses, according to the invention it is preferably possible to change or adjust the width of the N gaps present in the N sets of rollers. The width of the gap in each set of rollers may be changed either by changing the diameter of the rollers while keeping the distance between the two rollers constant, or by changing the distance between the rollers of this set (in which case the diameter of each roller of this set is kept constant). Other possibilities of changing the gap between the rollers of any set are included as well. By "distance" between a set of rollers is meant the distance between their axes of rotation. To change the diameter of the rollers, for example expandable / contractible rollers can be used. Also, the rollers of the first or second set are removable, allowing the selection of rollers with the desired diameter.

[0059] To change the distance between the rollers of the first set or between the rollers of the second set, one or both rollers of the set may be shifted along a suitable guide. Considering N sets of rollers defining N gaps with N widths, it is preferred that the widths of the N gaps decrease along the sheet transport direction. Thus, the first set of rollers defines a gap with the largest width, the second set of rollers (being the last set of rollers in the series of N sets of rollers in the sheet transport direction) has the smallest gap width, and the N-2 sets of rollers located between the first and second sets of rollers have a monotonically decreasing gap width comprised between the gap first width and the gap second width.

[0060] In the case of N rollers, the pressure applied to the sheet by the sets of rollers preferably increases from the first set of rollers having the lowest pressure to the second set of rollers (which are the last set of rollers in the row) having the highest pressure. The applied pressure preferably increases monotonically between those of the N-2 sets of rollers along the transport direction of the sheet.

[0061] The method preferably includes a step of drying the sheet during the compression step between the first set of rollers, or during the compression step between the second set of rollers, or between the compression steps between the first set of rollers and the second set of rollers. While the thickness of the sheet is adjusted by the compression in several steps, the sheet is preferably also dried. Thus, N sets of rollers are preferably included in the dryer. Drying is preferably achieved by a combination of a hot roller surface in direct contact with the sheet and a hot fluid present in the dryer. Each of the rollers of the first set of rollers or each of the rollers of the second set of rollers preferably defines a roller surface. The rollers of the first set of rollers or the rollers of the second set of rollers, or both, are heated by a hot fluid such as steam or vapor. Due to the hot fluid, the roller surface of the rollers of the first set of rollers or the roller surface of the rollers of the second set of rollers becomes hot. The temperature of the roller surface in contact with the drying sheet is preferably comprised between about 40 degrees Celsius and about 250 degrees Celsius, more preferably between about 120 degrees Celsius and about 200 degrees Celsius, or about 160 degrees Celsius. The temperature of the hot fluid (e.g., hot air) is preferably comprised between about 40 degrees Celsius and about 250 degrees Celsius, more preferably between about 120 degrees Celsius and about 200 degrees Celsius, or about 160 degrees Celsius.

[0062] In the case of N sets of rollers, it is preferred that all rollers of all sets are contained within the dryer, and thus a drying step is preferably performed between each of the N compression steps, and also while the sheet moves from one set or roller to the next set of rollers.

[0063] The compression step with any of the N sets of rollers also preferably improves the efficiency of the drying step. Typically, drying is performed with a hot fluid. Compression may squeeze out some of the water from the sheet, so that overall drying takes less time, or, as for the case where no compression is performed, a cooler fluid can be used for drying.

[0064] The method preferably includes adjusting the temperature of the first set of rollers or the second set of rollers. Drying may be further improved in efficiency by heating the rollers. Alternatively, the rollers can be cooled, for example the temperature of the set of rollers closer to the exit of the dryer can be reduced. The temperature of the rollers, depending on whether they are used for heating or cooling, is preferably comprised between about 10 degrees Celsius and about 250 degrees Celsius.

[0065] The step of forming the sheet preferably includes forming the sheet on a movable support, the movable support being moved by a first set of rollers. More preferably, the method includes a step of removing the sheet from the belt before the step of compressing the sheet between a second set of rollers. When formed by any method, the sheet is preferably positioned on a movable support due to its relatively high moisture content, which is between 50 percent and 80 percent. Without a support, the sheet may break while being "suspended" to reach the first set of rollers. For this reason, it is preferable to provide a movable support on which the sheet with a high moisture content can be placed and conveyed towards the first set of rollers. However, to improve the control of the drying of the sheet, it is preferable to remove the sheet from the support as soon as possible. In fact, the sheet on the support has one of its sides (the side in contact with the support) that may dry differently from the free side that is not in contact with the support. In order to obtain a homogeneous drying, and therefore a homogeneous sheet, the removal between the sheet and the support is carried out between two successive sets of rollers (for example a first set of rollers and a second set of rollers). In the case of N rollers, the removal of the sheet from the support is carried out between the first set of rollers and the (N-2)th set of rollers. In this way, optimal drying of the sheet may be achieved. A movable support is further used to move the sheet along the conveying direction. The movable support may for example be a conveyor belt. The surface of the belt in contact with the sheet is preferably realized in metal.

[0066] Prior to removing the sheet from the movable support, the method preferably includes the step of reducing the moisture content of the sheet to a value less than about 35 percent of the total weight of the sheet. In order to remove the sheet from the support while minimizing possible tearing or breakage of the sheet, the sheet is removed when the moisture content of the sheet is less than about 35 percent of its total weight. More preferably, the moisture content of the sheet at removal is preferably comprised between about 5 percent and about 30 percent of the total weight of the sheet. Even more preferably, the moisture content of the sheet is preferably comprised between about 7 percent and about 15 percent of the total weight of the sheet.

[0067] Prior to removing the sheet from the movable support, the method preferably includes the step of bringing the temperature of the sheet of alkaloid-containing material to about 100 degrees Celsius to about 150 degrees Celsius. It is preferred that the temperature of the sheet be within this interval to minimize damage to the sheet on removal from the support. The brittleness of the sheet may depend on both its moisture content and its temperature.

[0068] The invention also relates to an apparatus for producing a sheet of an alkaloid-containing material, the apparatus comprising a mixer for mixing the alkaloid-containing material with water to form a slurry, a sheet forming apparatus for forming a portion of the slurry into a sheet, and a dryer comprising a first set of rollers forming a first gap between which the sheet can be inserted and a second set of rollers forming a second gap between which the sheet can be inserted, the second set of rollers being positioned downstream of the first set of rollers in the direction of travel of the sheet.

[0069] The invention also relates to an apparatus for producing a sheet of an alkaloid-containing material, the apparatus comprising a mixer for mixing the alkaloid-containing material with water to form a slurry, a sheet forming apparatus for forming a portion of the slurry into a sheet, and a dryer comprising a first pair of rollers forming a first gap between which the sheet can be inserted and a second pair of rollers forming a second gap between which the sheet can be inserted, the second pair of rollers being positioned downstream of the first pair of rollers in the direction of travel of the sheet.

[0070] Many of the advantages of the present invention have been described previously and will not be repeated here. The apparatus of the present invention includes N sets of rollers (N is 2 or more) contained within a dryer. It is preferred that all of the N sets of rollers (N is 2 or more) are contained within a dryer. In some steps, compression of the sheet is performed while the sheet itself is drying. Efficient drying of the sheet is obtained while the desired final thickness is achieved.

[0071] The second gap is preferably smaller than the first gap. For N sets of rollers, the first set of rollers is closest to the sheet former and the second set of rollers is the last set of rollers in the row, the first gap of the first set of rollers is the largest in width and the second gap of the second set of rollers is the smallest. The remaining N-2 sets of rollers have gaps whose widths are comprised between the width of the first gap and the width of the second gap.

[0072] The first set of rollers preferably includes a first roller and a second roller, and the second set of rollers preferably includes a third roller and a fourth roller, and the diameter of the first roller is preferably larger than the diameter of the third roller. In the case of N rollers, the diameter of the rollers preferably decreases along the direction of the movement of the sheet. A better control of the thickness of the sheet is obtained. The decrease in the diameter of the rollers preferably determines a consequent decrease in the contact surface between the rollers and the sheet. More precise thickness adjustment and control can be achieved.

[0073] The diameter of the first roller is preferably equal to the diameter of the second roller.

[0074] The diameter of the third roller is preferably equal to the diameter of the fourth roller.

[0075] Preferably, the width of the gap between a pair of rollers is reduced, moving the two rollers closer together.

[0076] The first set of rollers includes a first roller and a second roller, and the second set of rollers includes a third roller and a fourth roller, and the external surface of the third roller preferably has a higher hardness than the external surface of the first roller. Hardness is a measure of resistance to localized plastic deformation induced by either mechanical indentation or wear. Some materials are harder than others. Depending on the material of the roller, the curing process and, as a result, the final hardness of the roller will vary. Depending on the material, the rollers may have different hardnesses. For steel rollers, the hardness is preferably comprised between about 1 and about 50 HRC (Rockwell scale), for plastic rollers, the hardness is preferably comprised between about D10 and about D100 (Shore durometer), and for rubber rollers, the hardness is preferably comprised between about A10 and about A100 (Shore durometer). The rollers can be made of metal, plastic, or rubber. The surfaces of the first set of rollers or the second set of rollers can be coated with layers of different materials having different hardness. In the case of N sets of rollers, the hardness of the sets of rollers preferably increases in the conveying direction of the sheet from the first set of rollers to the Nth set of rollers.

[0077] The hardness of the first roller is preferably equal to the hardness of the second roller.

[0078] The hardness of the third roller is preferably equal to the hardness of the fourth roller.

[0079] The device comprises a movable support, which is preferably driven by the first roller or the second roller of the first set of rollers. The movable support is preferably present for transporting the sheet along the transport direction. The movable support is preferably driven by one of the rollers of the first set of rollers. The movable support preferably ends after the first set of rollers. In case of N pairs of rollers, the movable support preferably extends in the transport direction of the sheet passing through a given number of sets of rollers. After the first set of rollers or the second set of rollers, the sheet is "rigid enough" so that it is self-supporting and is driven at least by the motorized set of rollers to the next roller. The movable support preferably ends between the first set of rollers and the second set of rollers.

[0080] Specific embodiments are further described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0081] [Figure 1] FIG. 1 shows a flow diagram of a method for producing a slurry for homogenized tobacco material according to the present invention. [Diagram 2] FIG. 2 shows a block diagram of a process for the production of homogenized tobacco material according to the present invention. [Diagram 3] FIG. 3 shows an apparatus for the production of homogenized tobacco material according to the present invention. [Figure 4] FIG. 4 shows details of an apparatus for the production of homogenized tobacco material according to the present invention. [Diagram 5] FIG. 5 shows a schematic diagram of an apparatus for carrying out the method of FIGS. [Figure 6] FIG. 6 shows a schematic diagram of an apparatus for carrying out the method of FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0082] Referring initially to Figure 1, a method for producing a sheet of alkaloid-containing material, in this example a homogenized tobacco sheet, from a slurry according to the present invention is depicted. The first step in the method of the present invention is the selection 100 of the tobacco type and grade to be used in the tobacco blend to produce the homogenized tobacco material. The tobacco types and grades used in the method include, for example, bright tobacco, dark tobacco, aromatic tobacco, and filler tobacco.

[0083] Only selected tobacco types and grades that are intended for use in the manufacture of homogenized tobacco material undergo processing according to the following steps of the method of the present invention.

[0084] The method includes a further step 101 of laying down the selected tobacco. This step may include checking the integrity of the tobacco, such as grade and quantity, which can be verified, for example, by a barcode reader for product tracking and traceability. After harvesting and curing processes, tobacco leaves are given a grade that describes the stem position, quality, and color.

[0085] Additionally, if the tobacco is to be shipped to a manufacturing facility for the production of homogenized tobacco material, the laying step 101 may also include the step of unpacking or uncasing the tobacco packets. The unpacked tobacco is then preferably provided to a weighing station for weighing the tobacco.

[0086] Furthermore, because tobacco leaves are typically transported in bales when packed and shipped, the step 101 of laying the tobacco may include opening the bales, if necessary.

[0087] The bales of tobacco are separated according to tobacco type. For example, there may be a processing line for each tobacco type. Thus, the following steps are performed for each tobacco type, as detailed below. These steps may be performed sequentially grade by grade, so that only one production line is required. Alternatively, different tobacco types may be processed in separate lines. This may be advantageous if the processing steps for some tobacco types are different. For example, in conventional primary tobacco processes, dark tobacco often receives an additional casing, while bright and dark tobacco are at least partially processed in separate processes. However, according to the present invention, it is preferred not to add casing to the blended tobacco powder prior to the formation of the homogenized tobacco web.

[0088] The method of the present invention further includes a step 102 of coarsely grinding the tobacco leaves.

[0089] According to a variant of the method of the invention, after the step 101 of laying the tobacco and before the step 102 of coarsely grinding the tobacco, a further shredding step (not shown) is carried out. In the shredding step, the tobacco is shredded into pieces with an average size of about 1 millimeter to about 100 millimeters.

[0090] After the shredding step, it is preferred to carry out a step of removing non-tobacco material from the strips (not shown in FIG. 1).

[0091] The shredded tobacco is then conveyed to a coarse grinding step 102. It is preferred to control and meter the rate at which tobacco flows into the mill for coarse grinding into small pieces of tobacco.

[0092] In the coarse grinding step 102, the tobacco shreds are reduced to a particle size of about 0.25 millimeters to about 2 millimeters. At this stage, the tobacco particles still have their cells substantially intact and the resulting particles do not pose the associated transport problems.

[0093] After the coarsely grinding step 102, the tobacco particles are preferably conveyed (e.g., by pneumatic movement) to a blending step 103. Alternatively, the blending step 103 can be performed before the coarsely grinding step 102, or before the shredding step, if present, or alternatively, the blending step 103 can be performed between the shredding step and the coarsely grinding step 102.

[0094] In the blending step 103, all the coarsely ground tobacco particles of the different tobacco types selected for the tobacco blend are blended. Thus, the blending step 103 is a single step for all the selected tobacco types. This means that after the blending step, only a single process line for all the different tobacco types is needed.

[0095] The blending step 103 preferably involves a mixture of various tobacco types in particulate form.

[0096] After the blending step 103, a pulverizing step 104 is performed to a tobacco powder size of about 0.03 millimeters to about 0.12 millimeters. The pulverizing step 104 reduces the size of the tobacco to a powder size suitable for preparation of a slurry. After the pulverizing step 104, the tobacco cells are at least partially destroyed and the tobacco powder may become sticky.

[0097] The tobacco powder thus obtained can be immediately used to form a tobacco slurry, or alternatively, a further step of storage of the tobacco powder, for example in a suitable container, may be inserted (not shown).

[0098] Now referring to FIG. 2, the method of the present invention for the manufacture of a homogenized tobacco web is shown. From the fine grinding step 104, the tobacco powder is used in a subsequent slurry preparation step 105. Before or during the slurry preparation step 105, the method of the present invention comprises two further steps; a pulp preparation step 106, in which the cellulose fibers 5 and water 6 are pulped in order to purify the cellulose fibers by dispersing them homogeneously in the water, and a suspension preparation step 107, in which an aerosol former 7 and a binder 8 are premixed. The aerosol former 7 preferably comprises glycerol and the binder 8 preferably comprises guar. Advantageously, the suspension preparation step 107 comprises premixing guar and glycerol without introducing water.

[0099] The slurry preparation step 105 preferably includes transferring a premixed solution of aerosol former and binder to a slurry mix tank and transferring pulp to the slurry mix tank. Additionally, the slurry preparation step includes dosing a tobacco powder blend into the slurry mix tank with the pulp and dosing a suspension of guar and glycerol. More preferably, this step also includes processing the slurry using a high shear mixer to ensure uniformity and homogeneity of the slurry.

[0100] The slurry preparation step 105 also preferably includes the step of adding water, where water is added to the slurry to obtain the desired viscosity and moisture content.

[0101] To form a homogenized tobacco web, the slurry formed by step 105 is preferably delivered to a casting box where the slurry is mixed and then cast in a casting step 108. The casting step 108 preferably includes delivering the slurry to a casting station and casting the slurry into a web on a support. During casting, the thickness, moisture, and density of the cast web are preferably controlled immediately after casting, and more preferably continuously monitored and feedback controlled during the process using a slurry measurement device.

[0102] The desired thickness of the sheet is preferably selected.

[0103] The homogenized cast web is then dried in a drying step 111 which involves uniform and gentle drying of the cast web, for example on an endless stainless steel belt, which may comprise individually controllable zones. The drying step preferably includes monitoring the cast leaf temperature in each drying zone to ensure a gentle drying profile in each drying zone, and heating the support on which the homogenized cast web is formed. The drying profile is preferably a so-called TLC drying profile.

[0104] During the drying step 111, a first compression step 109 and a second compression step 110 are performed. The first and second compression steps are successive to one another. The first compression step is performed while the sheet is on the belt. The compression is achieved between two rollers forming a first gap between them, into which the sheet is inserted and compressed. After the first compression, the sheet may be removed from the belt, so that it is then free-standing. The sheet undergoes a second compression step between these two rollers, which also form a second gap between them. The second gap is preferably smaller than the first gap. This second compression is preferably performed while drying is also taking place. There is also preferably a third compression step 110a between the first and second compression steps, using a third set of two rollers forming a third gap between the rollers, which is preferably smaller than the first gap but larger than the second gap. The third compression step is also preferably performed during drying. At the end of the compression steps, a sheet of the desired thickness is obtained. This thickness may be further altered by the drying process.

[0105] At the end of the web drying step 111, a monitoring step (not shown) is performed to measure the moisture content in the dried web and the number of defects present.

[0106] The homogenized tobacco web, dried to a target moisture content, is then preferably wound in a winding step 112, for example to form a single master bobbin. This master bobbin may then be used to effect the manufacture of smaller bobbins by slitting the process to form smaller bobbins. The smaller bobbins may then be used for the manufacture of aerosol-generating articles (not shown).

[0107] If a sheet having a different thickness is desired in further processing, the distance between the rollers used in the first, second and third compression steps may be varied, i.e. the width of the first, second and third gaps may be varied to vary the thickness of the sheet after the drying step 111.

[0108] The method of production of a slurry for homogenized tobacco material according to Figure 1 is carried out using an apparatus 200 for slurry production, depicted diagrammatically in Figure 3. The apparatus 200 comprises a tobacco receiving station 201, where stacking, transshipment, weighing and inspection of different tobacco types takes place. Optionally, if the tobacco has been shipped in cartons, removal of the cartons containing the tobacco takes place at the receiving station 201. The tobacco receiving station 201 also optionally comprises a tobacco bale packing dividing unit.

[0109] In FIG. 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. The tobacco is further introduced into a shredder 202 for the shredding step. The shredder 202 may be, for example, a pin shredder. The shredder 202 is preferably adapted to handle bales of all sizes, so as to loosen the tobacco shreds and shred them into smaller pieces. The shredded tobacco pieces in each production line are conveyed, for example by a pneumatic conveyance 203, to a mill 204 for the coarse grinding step 102. Preferably, control is exercised during conveyance so that foreign objects in the shredded tobacco pieces are removed. For example, along the pneumatic conveyance of the shredded tobacco there may be a string removal conveyor system, a heavy particle separator, and a metal detector, all of which are indicated at 205 in the attached drawings.

[0110] The mill 204 is adapted to coarsely grind the tobacco shreds to a size between about 0.25 millimeters and about 2 millimeters. The mill rotor speed can be controlled and can be varied based on the tobacco shred flow rate.

[0111] A buffer silo 206 for uniform mass flow control is preferably located after the coarse crusher mill 204. Additionally, the mill 204 is preferably equipped with a spark detector and safety shutdown system 207 for safety reasons.

[0112] Tobacco particles are conveyed from the mill 204 to a blender 210, for example by a pneumatic conveyance 208. The blender 210 preferably includes a silo in which there is an appropriate valve control system. All tobacco particles of all the different types of tobacco selected for a given blend are introduced into the blender. In the blender 210, the tobacco particles are mixed into a uniform blend. The tobacco particle blend is conveyed from the blender 210 to a fine grinding station 211.

[0113] The fine grinding station 211 is, for example, an impact classification mill with appropriately designed auxiliary equipment to produce fine tobacco powder of the correct specification, i.e., about 0.03 mm to about 0.12 mm. After the fine grinding station 211, a pneumatic transfer line 212 is fitted to convey the fine tobacco powder to a buffer powder silo 213 for continuous feeding to a downstream slurry batch mixing tank where the slurry preparation process takes place.

[0114] The slurry prepared using the tobacco powder described above in steps 100-105 of the method of the present invention is also preferably cast in a casting station 300 as depicted in FIG.

[0115] The slurry (not shown) from the buffer tank is transferred to the casting station 300 by a suitable pump with precision flow control metering. The casting station 300 preferably comprises the following sections: A precision slurry casting box and knife assembly 301 receives the slurry from the pump, where the slurry 11 is cast onto a support 303, such as a stainless steel belt, with the uniformity and thickness required for proper web formation. A primary dryer 302 having a drying zone or section is provided to dry the cast tobacco web. A separate drying zone preferably has steam heating below the support, with heated air above the support and adjustable exhaust control. Within the primary dryer 302, the homogenized tobacco web is dried onto the support 303 to the desired final moisture.

[0116] Referring now to more detailed Figure 5, further details of the casting station 300 are shown. A precision slurry casting box and knife assembly 301 includes a casting blade 304 and a casting box 305. A moveable support 303 includes a continuous stainless steel belt that comprises a drum assembly. The steel belt 303 is preferably wrapped around a pair of opposing drums 306, 307. The slurry is cast (at drum 306) through the casting blade 304 and onto the steel belt, which creates a continuous sheet 10 of homogenized tobacco material.

[0117] The cast slurry 10 is driven by steel belt 303 along a casting or conveying direction indicated by arrow 24 in Figure 5 and enters dryer 302 where it is gradually heated and uniformly dried. In Figure 5, dryer 302 is only partially depicted.

[0118] The incoming slurry 11 is introduced into the casting box 305 through an inlet (not shown) (specifically a pipe) connected to the side wall 14 of the casting box 305, which places the incoming slurry 11 adjacent to the bottom of the casting box 305.

[0119] Slurry 11 from a buffer tank (not shown in the drawings) is typically moved into the casting box 305 by a pump (not shown in the drawings). The pump is preferably equipped with a flow control (not visible in the drawings) to control the amount of slurry 11 introduced into the casting box 305. The pump is advantageously designed to ensure that slurry transfer times are kept to a necessary minimum.

[0120] The amount of slurry 11 in the casting box 305 has a predetermined level, which is preferably kept substantially constant or within a given range. To keep the amount of slurry 11 at substantially the same level, a pump controls the flow of slurry 11 into the casting box 305.

[0121] A casting blade 304 is associated with a casting box 305 for casting the slurry. The casting blade 304 has a major dimension that is its width along its longitudinal axis. The casting blade defines a first axis that is positioned along its longitudinal axis.

[0122] Between the casting blade 304 and the steel belt 303 there exists a gap, the dimension of which determines, among other things, the initial thickness of the cast web 10 of homogenized tobacco material at the time of casting, called initial thickness. This initial thickness is preferably checked, for example, by a suitable sensor 15 (visible in Figure 4), preferably having a feedback loop with the casting blade 304. The gap formed between the casting blade and the steel belt may be corrected based on the signal output by the sensor 15 (see Figure 4).

[0123] Casting blade 304 and belt 303 face each other, and the belt is positioned partially below casting blade 304. Drum 306 carries and preferably rotates belt 303 in the direction depicted by arrows 24 and 26.

[0124] The casting station 300 also includes a first set of rollers 310 formed by a second drum 307 as a first roller and a second roller 308. The first roller 307 and the second roller 308 form a first gap 311 therebetween.

[0125] The belt is also wrapped around a second drum 307. The second drum 307 forms part of a first set of rollers 310, the first roller 307 being the second drum and the second roller 308 being positioned vertically above the first roller 307. The two rollers form a first gap 311 between them and have a variable thickness. The first set of rollers 310 is positioned inside the dryer 302. The sheet is inserted into the gap 311 and compressed, which removes water from the sheet. The thickness of the sheet after the first set of rollers 310 is called the first thickness, which is denoted by t1. The first set of rollers 310 is the first of N sets of rollers, where N is 2 or more. In FIG. 6, an example is shown where N=3 sets of rollers. The casting station 300 includes a first set of rollers 310, a second set of rollers 312 (the last pair before the sheet exits the dryer 302), and a third set of rollers 313 positioned between the first and second sets of rollers. Each set of rollers defines a gap between the rollers forming that set. The second set of rollers 312 includes a third roller 316 and a fourth roller 317 that form a second gap 318 therebetween. The thickness of the sheet after the second set of rollers is referred to as the third thickness and is designated t2. The third set of rollers 313 includes a fifth roller 319 and a sixth roller 320 that form a third gap 321 therebetween. The thickness of the sheet after the third set of rollers is referred to as the third thickness and is designated t3. The width of the gap between the rollers of the set decreases monotonically from the first set of rollers to the second set of rollers, i.e., the width of the first gap 311 is greater than the width of the third gap 321 which is greater than the width of the second gap 318. Similarly, the first thickness of the sheet 10 decreases from its thickest t1 after the first set of rollers 310 to its thinnest t2 after the second set of rollers 312.

[0126] In other words, t1>t3>t2. Preferably, one or more of the rollers of the sets 310, 312, 313 positioned below the sheet 10 can vary their diameter.

[0127] The diameter of the rollers also preferably decreases from the first set of rollers 310 to the second set of rollers 312 (which have the smallest diameter). The third set of rollers 313 has an intermediate diameter between the first and second set of rollers.

[0128] The thickness t2 of the sheet after the second set of rollers 312 is preferably checked by a suitable sensor 16 (see FIG. 4), for example positioned downstream of the dryer 302 in the direction of movement of the belt 303. A feedback loop preferably exists between the sensor 16 checking the thickness t3 and the first gap 311, the second gap 318 and the third gap 321 between the first set of rollers 310, the second set of rollers 312 and the third set of rollers 313. These gaps can be adjusted according to the signal sent by the sensor 16.

[0129] Downstream of the dryer 302, the dried sheet can be wound onto a bobbin (not shown) for storage or can be further used to manufacture aerosol-generating articles.

Claims

1. 1. A method for producing a sheet of alkaloid-containing material comprising the steps of: mixing an alkaloid-containing material with water to form a slurry; forming a sheet from the slurry; compressing the sheet between a first pair of rollers, wherein at the start of the step of compressing the sheet, the moisture content of the sheet comprises between about 50 percent and about 80 percent of the total weight of the sheet; and further compressing the sheet compressed by the first pair of rollers between a second pair of rollers to obtain a desired thickness of the sheet of alkaloid-containing material.

2. The method of claim 1 , wherein the step of forming a sheet comprises the step of casting a sheet.

3. The method of claim 1 , wherein the step of forming a sheet comprises the step of extruding the sheet.

4. the first pair of rollers includes a first roller and a second roller forming a first gap therebetween, and the second pair of rollers includes a third roller and a fourth roller forming a second gap therebetween; A method according to any of claims 1 to 3, comprising the step of varying the width of the first gap or the width of the second gap.

5. varying the diameter of one roller of the first pair of rollers or the diameter of one roller of the second pair of rollers depending on the desired thickness of the sheet containing alkaloid, or o A method according to claim 4, comprising the step of varying the distance between the first roller and the second roller or varying the distance between the third roller and the fourth roller depending on the desired thickness of the sheet containing alkaloid.

6. A method according to any of the preceding claims, comprising a step of drying the sheet during the compressing step between the first pair of rollers, or during the compressing step between the second pair of rollers, or between the compressing step between the first pair of rollers and the compressing step between the second pair of rollers.

7. A method according to any of the preceding claims, comprising the step of adjusting the temperature of the first pair of rollers or the temperature of the second pair of rollers.

8. The step of forming the sheet comprises: A method according to any of the preceding claims, comprising the step of forming the sheet on a movable support, the movable support being moved by the first pair of rollers.

9. o The method of claim 8, comprising the step of removing the sheet from the movable support prior to the step of compressing the sheet between the second pair of rollers.

10. Prior to removing the sheet from the movable support, 10. The method of claim 9, comprising reducing the moisture content of the sheet to a value less than about 35 percent of the total weight of the sheet.

11. 1. An apparatus for producing sheets of alkaloid-containing material, comprising: a mixer for mixing the alkaloid-containing material with water to form a slurry; a sheet former for forming the slurry portion into a sheet; A dryer, a first pair of rollers that form a first gap between the rollers and into which the sheet can be inserted; a second pair of rollers that forms a second gap between the rollers and into which the sheet can be inserted, the second pair of rollers being positioned downstream of the first pair of rollers in the direction of movement of the sheet; a dryer including the first pair of rollers or the second pair of rollers, the first pair of rollers being heated by a high-temperature fluid; the first pair of rollers includes a first roller and a second roller, and the second pair of rollers includes a third roller and a fourth roller, and the diameter of the first roller is greater than the diameter of the third roller; Device.

12. An apparatus for producing sheets of alkaloid-containing material comprising: a mixer for mixing the alkaloid-containing material with water to form a slurry; a sheet former for forming the slurry portion into a sheet; A dryer, a first pair of rollers that form a first gap between the rollers and into which the sheet can be inserted; a second pair of rollers that forms a second gap between the rollers and into which the sheet can be inserted, the second pair of rollers being positioned downstream of the first pair of rollers in the direction of movement of the sheet; a dryer including the first pair of rollers or the second pair of rollers, the first pair of rollers being heated by a high-temperature fluid; the first pair of rollers includes a first roller and a second roller, and the second pair of rollers includes a third roller and a fourth roller, and the outer surface of the third roller has a higher hardness than the outer surface of the first roller; Device.

13. An apparatus for producing sheets of alkaloid-containing material comprising: a mixer for mixing the alkaloid-containing material with water to form a slurry; a sheet former for forming the slurry portion into a sheet; A dryer, a first pair of rollers that form a first gap between the rollers and into which the sheet can be inserted; a second pair of rollers that forms a second gap between the rollers and into which the sheet can be inserted, the second pair of rollers being positioned downstream of the first pair of rollers in the direction of movement of the sheet; a dryer including the first pair of rollers or the second pair of rollers, the first pair of rollers being heated by a high-temperature fluid; a movable support, the movable support being driven by a first roller or by a second roller of the first pair of rollers; Device.

14. The apparatus of any one of claims 11 to 13, wherein the second gap is smaller than the first gap.

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